mortality and fertility of european charadrii

368 HUGH BOYD : MORTALITY AND FERTILITY OF CHARADRII IBIS 104

MORTALITY AND FERTILITY OF EUROPEAN CHARADRII

HUGH BOYD

Received on 2 November 1961

CONTENTS INTRODUCTION SUGGESTIONS FOR FURTHER INQUIRIES CALCULATION OF MORTALITY-RATES SUMMARY CALCULATION OF FERTILITY REFERENCES NOTES ON THE SPECIFIC ESTIMATES APPENDIX. TABLES OF MORTALITY AND FERTILITY MORTALITY AND TAXONOMIC RELATIONSHIPS STATISTICS MORTALITY AND BODY-SIZE

INTRODUCTION

This is a preliminary review of the population dynamics of wading birds (Order Charadriiformes, sub-order Charadrii), based on studies of European species. The foundations are provided by estimates of specific annual death-rates derived from recoveries of ringed birds. The information on mortality is complemented by published data on the fertility of intensively-studied populations. These data and their relationships are then discussed with reference to taxonomic affinities within the group and in comparison with a recent account of the population dynamics of the Anatidae.

Several papers appearing in recent years have dealt with the mortality experience of single species of waders. Most of these studies have been concerned as much with technical difficulties in estimating population parameters from recoveries as with the biological significance of the results. In this review comment on technical problems has deliberately been kept to a minimum.

I am indebted to the Bird Ringing Committee of the British Trust for Ornithology for permission to consult unpublished ringing and recovery records and to R. Spencer, Ringing Officer, for his help. Dr. G. V. T. Matthews read several drafts of this paper with critical care and I am grateful for his advice, and for that of S. M. Taylor on some statistical problems.

P. E. Brown and P. J. Conder, of the Royal Society for the Protection of Birds, kindly provided unpublished details of the breeding success of Avocets in England.

CALCULATION OF MORTALITY-RATES

This paper contains estimates of the mean annual adult death-rates of 23 species. In this context " adult " refers to individuals more than one year old, irrespective of whether such birds have attained sexual maturity. For most species separate estimates of mortality in the first year after fledging are also given. The data consist of the recoveries published by most European schemes, supplemented by unpublished records in the files of the Bird Ringing Office of the British Trust for Ornithology. The publications examined differ in no important particulars from those used and listed by Nsrrevang (1959) with the addition of several published between 1958 and 1961. Of these the most important new source is the series ' Auspicium ' devoted to results obtained by Vogelwarte Helgoland and Vogelwarte Radolfzell.

Many of the specific samples are heterogeneous with respect to the country of marking and the probable breeding areas from which they were drawn. For those species of which recoveries are plentiful, results from small-scale ringing in some countries have been omitted from the calculations.

For individuals ringed as nestlings the breeding areas are, of course, the same as the places of marking. For those ringed as passage migrants the probable breeding areas are noted, so far as they are known; the source of information is the review by Nsrrevang (1959) unless otherwise stated.

1962 HUGH BOYD : MORTALITY AND FERTILITY OF CHARADRII 369

In nearly every case the method of estimating adult mortality is that of Lack (1943 a), supplemented by Haldane’s (1955) procedures for estimating the standard error and for correcting “ incomplete data ” in which an appreciable proportion of the probable total recoveries from a ringed sample were still alive and unreported at the time the latest recovery lists were compiled. Two methods of grouping recoveries according to the interval between marking and recovery are used. In some cases the time intervals are years from the date of marking of each individual. In others the intervals are calendar years from the first 1 January after marking. The grouping used is recorded in each case, as “ from marking ” or “ calendar years ” respectively. The chosen method is that which provides the largest recovery series compatible with the need to eliminate the effects of greater vulnerability among young birds, where this appears to exist. The selection of the closing-date for ringing and recoveries has also been determined by aiming at the largest recovery-series compatible with the limits imposed by delays in the publication of recovery records.

Estimates of mortality based on live recaptures of marked birds are included for a few species. These are calculated by the procedure described as “Method By’ by Leslie & Chitty (1951), in which recaptures are grouped according to the interval of time since they were last captured.

The usual procedure adopted in estimating mortality in the first year after fledging among birds ringed as nestlings is as follows. Recoveries where ringed and very soon after marking are rejected, as belonging to pre-fledging losses. An index of first year mortality (dl) is given by the number of recoveries in the first year after marking expressed as a percentage of the total recoveries reported, using years remote enough to allow of a negligible proportion of present-day survivors. In some species juveniles ringed in late summer are used instead of nestlings in this calculation. The lack of coincidence of the time of ringing with the time of fledging obviously affects the reliability of the index. Since in most species juveniles seem to be more vulnerable than older birds to shooting and trapping, and provide most of the recoveries (Table l) , the index is also biased to

TABLE 1. The proportion of recoveries of ringed European Charadrii reported as deliberately killed by man.

Species

Oystercatcher

Ringed Plover

Golden Plover Turnstone Common Snipe

Woodcock Curlew Black-tailed Godwit Wood Sandpiper Common Sandpiper Common Redshank

Knot Dunlin Curlew Sandpiper and

Ruff Avocet

Sanderling

Where ringed Number of reports stating cause

of death first year older

Continental Europe Gt. Britain Continental Europe Gt. Britain Iceland, Scandinavia Scandinavia Continental Europe Gt. Britain All sources All sources All sources Sweden All sources Scandinavia Gt. Britain Scandinavia Sweden

All sources All sources All sources

55 44 71 56 58 44 31 24 32 27 52 31 27 3 1 48 125

253 207 145 114

21 44 72 3 1

32

25 25 84 48

105 168

134 23 101

Proportion killed by man (%)

first year older

55 43 18 34 83 80 45 42 81 85 88 81 93 90 86 84 91 92 60 65 95 82 93 77 61 47 89 85 48 44 88 79 84 75

28 23 89 83 34 45 91 73 94 50 82 76


exaggerate first year losses. Myhrberg (1961) has discussed an extreme example in the Wood Sandpiper. In those few cases where the estimated juvenile vulnerability is very different from the adult value, d, is expressed as a range rather than a single value, the smaller figure being obtained by mukiplying d, by the ratio (proportion of older birds killed by man) : (proportion of first year birds killed).

CALCULATION OF FERTILITY

The available information on the breeding success and early survival of waders is meagre. For a comparative study such as this, it is necessary to convert published material into a common form, so far as this may be practicable. The procedure followed here is to arrive at an estimate of net fertility from separate estimates of egg production, hatching success, fledging success and the survival of fledged young to maturity. Net fertility is defined in the following way (by Capildeo & Haldane 1954): " If N adult females produce so many eggs that fsN of their female progeny are alive at the time of laying in the next year, then f is the net fertility ", s being the adult survival rate (= 1 - d, the mortality-rate). In the case of a bird maturing at a years the requirement is that the fertility and mortality of eggs and young birds be such that, on average, fsa female progeny per adult female per year reach the age of maturity.

In this paper, f is determined from the equation f =c u v s1/2s, where c is the mean number of eggs laid by a female in a year, u is the fraction of eggs laid which hatch, v is the fraction of eggs hatched from which young are reared to full-size and s, is the survival rate in the first year after fledging. s1 is less than the true survival rate (say sl) for the interval between fledging and the beginning of the next breeding season, because that interval is less than a full year. But at the level of accuracy of this enquiry no serious error seems likely to result from using s, (= 1 - dl) instead of sl, which would be difficult to determine. The figure 2 in the denominator expresses the assumption that the sex- ratio in fertile eggs is close to unity. c is usually greater than the mean clutch-size: some species habitually lay two clutches a season and most are able to re-nest at least once if the first nest is destroyed. u is relatively easy to determine, though it may vary greatly from year to year or colony to colony. w is difficult to obtain for nidifugous species and uncertainty on this point is the most obvious and serious weakness of the data which follow.

SPECIFIC ESTIMATES

In order to reduce tedious repetition in the text, all the calculated statistics have been assembled in tabular form in the Appendix. The estimates for the Oystercatcher are discussed at some length in the text by way of example. Otherwise the notes which follow are intended as a commentary on the Appendix, only those procedures which are not standard being set out in detail.

OYSTERCATCHER Haematopus ostralegus. Mortality. There is an important difference between the apparent adult death-rate

of Oystercatchers ringed in Holland and those ringed in Britain and Scandinavia. German recoveries have not been published in full, so that similar calculations cannot be made. However, two papers have been published which give information on the survival of adult Oystercatchers on the German island sanctuary of Mellum, where most of the breeding birds have been ringed for many years. Drost & Hartmann (1949) noted that in 1949 11 of 32 adults recaptured after ringing in earlier years were more than 15 years old. They put the average age of the breeding population at nearly 10 years. Jungfer (1954) discussed the persistence of the pair bond and the tendency to return to the same breeding area among these Mellum birds. From the details of ringing and recaptures


which he gives it is possible to determine the annual death-rate among adults breeding on Mellum in the period 1949-53, by means of a capture-recapture calculation using each whole season as a unit in a five-point series. This yields an estimated death-rate of 14.0+4.3%. Thus the German estimate is consistent with the Dutch, but much smaller than the apparent rate of loss of other ringed samples. Buxton (1957) pointed out that a satisfactory estimate of mortality could not be obtained from the recoveries of British-ringed Oystercatchers because there is evidence of loss of rings from still living birds, due to weakening of the metal by wear. (This situation may have been remedied in recent years by the use of monel, in place of aluminium, rings.) Though the reports of the Scandinavian ringing schemes do not provide explicit evidence of such losses of their rings, it seems likely that they have occurred. No British-ringed Oystercatcher has been found more than 11 years after marking, no Scandinavian-ringed more than 9, whereas 14 Dutch rings have lasted more than 11, one of them more than 27 years.

Using only the Dutch recovery series for ringing up to 1950, the index of mortality in the first year from fledging is 36%. The recoveries in later years of life are in extremely close agreement with those expected on the hypothesis that after the first year the death- rate does not vary with age for at least the next 15 years.

There do not seem to have been any marked differences in the death-rate of Dutch- ringed birds between five-year periods in the years 1925-56. The numbers of recoveries are too small to give useful estimates of possible fluctuations between one year and another.

The Oystercatcher is the only species listed in Table 1 for which less than half the recoveries reported have been due to hunting by man. The proportion deliberately killed is particularly low in the British sample. The strikingly low proportion of casualties attributed to man among British Oystercatchers in their first year is perhaps a reflection of a high reporting rate for other types of casualty rather than of an especially low kill. So many factors are liable to affect reporting that clarification of this point is not possible.

Fertility. The clutch-size of the Oystercatcher, which seems to be subject to regional variation, has received considerable attention, but few studies have dealt with nesting success. The two most important are the long continued investigations on Skokholm (Keighley & Buxton 1948, Keighley 1949, Neddermann 1954) and those of Dircksen (1932) on the north German island of Norderoog.

Estimates of egg output (c), hatching and fledging success (u and v) and first year survival (sl) are required. From the combined published results for Skokholm the values of c and u are about 2-67 and 0.66. The determination of is especially difficult for a species like the Oystercatcher whose young are taken away from the immediate vicinity of the nest-site, usually into a different ecological zone. Keighley (1949) provides the only estimate of v for Skokholm birds, recording that in 1948 it was equal to or less than 64/74 (=0*86) and that over several years it was probably about 0.75 (figure derived by the present writer). Thus the value of c u v is about 1.33, this being the average number of young reared by each breeding female.

No direct estimates of s1 or s are available for Skokholm birds, despite the extensive ringing of young Oystercatchers on the island. Since, however, the ratio of recoveries in the first year after ringing to that in the second year (45/11=4*1) is close to that given by Dutch Fnging (66/17= 3.9), it seems justifiable to assume that the ratio s,/s given by Dutch recoveries, 0*64/0.84= 0.76, could be applied to Skokholm birds. Estimates of the number of breeding pairs of Oystercatchers on the island in the years 1946-1960, tabulated in the Annual Reports of the Observatory for 1959 and 1960, show that the population has averaged about 48 pairs, fluctuating between the comparatively narrow limits of 35 and 54 pairs without any marked trends. Thus it can be taken to be in equilibrium.


The age at which Oystercatchers become mature (u) is apparently 3 years (Dircksen 1932, confirmed by later writers). For a species for which u=3, the estimates of fertility and survival of a population in equilibrium should satisfy the equation f=( 1 -s)/s3

(Capildeo & Haldane 1954). Using the values for c, u, v and sl/s given above to determine f, the corresponding value of s is 0.87. Thus the mean annual mortality of adult Oystercatchers in the Skokholm population is calculated to be 13%, close to the estimates given earlier for ringed birds on Mellum and for the mixed stocks ringed in the Nether- lands. Of the components used in this calculation, the value of v is most in doubt. I t is worth remarking that if the figure of 0.75 is too high, the breeding population on Skokholm could only have remained steady either because the mortality of adults was even less than 13% or because immigration exceeded emigration. There is no evidence to suggest a continuing surplus of mature immigrants.

Dircksen’s results on Norderoog showed one very striking difference from the Skokholm figures. c and u were both higher than for Skokholm (3.01 and 0.79 respectively), but the proportion of hatched young reared was extraordinarily low, only 3.6% of the eggs laid producing fledged young (for u=0.79 this makes v=0.046). Admittedly this result was obtained from thorough search in only one year, but in a more recent book Dircksen (1950) does not seek to amend it in the light of his later studies. Srhulz (1947) confirms that the output of fledged young on Norderoog and other North German islands appears to be very low. The estimated mortality of the breeding birds on Mellum is 14% (see above) so that for these populations of Mellum and Norderoog to remain steady the number of young reared per female must be about the same as that estimated for Skokholm. Schulz has tabulated the breeding population of Oystercatchers and other species nesting on German island bird sanctuaries, including Norderoog and Mellum. The Norderoog colony, which was the biggest in Germany, declined fairly steadily from 289 pairs in 1926 to 232 pairs in 1945, the estimated steady annual rate of decrease being 0.22%. Using this rate, the Mellum adult mortality rate, an sl/s ratio of 0.76 and Dircksen’s estimates of c and u it can be shown that the average value of v for Norderoog should have been about 0.24 instead of 0.406. This implies very substantial, but not catastrophic, losses amongst young birds before fledging. Both Dircksen and Schulz record that difficulties in food-finding in the days soon after hatching are the principal cause of loss, aggravated in some years by flooding of the low-lying breeding areas.

In the &and archipelago, Finland, Nordberg (1950) found c=2.88 from observations over 30 years. Nesting results in a single year gave u=0.92 and v=0.78 (29 fledged from 37 hatched). This is of interest in confirming that substantial rearing success is sometimes possible and that the German findings should not be taken as typical.

LAPWING Vunellus vanellus 1.06% obtained by Haldane (1955) from

recoveries of British-ringed Lapwings seems adequately to represent the mortality among steady populations throughout the range of the species in northwestern Europe, although some different figures have been published, notably 40% among Dutch-ringed birds according to Kraak, Rinkel & Hoogerheide (1940) and Klomp (1946). A comparative study of mortality estimates from ringing in different countries will be made in another paper.

Fertility. Although the breeding behaviour and biology of the Lapwing have been the object of much research, none of the published studies provides really good data for this review. There is a paucity of information on fledging success, which is not at all surprising to anyone who has attempted to watch young Lapwings. The results from Skokholm cited here (Vernon 1953) may have been rather unusual for that island, where in many years the proportion of eggs hatching successfully, while not recorded precisely, has evidently been much lower. The German colony studied for two years by Laven

Mortality. The adult death-rate of 34.29


(1941) was remarkably unsuccessful, due to heavy destruction of eggs by crows. The data gleaned from a report by Glutz (1959) on long-term fluctuations in the size of the Swiss breeding population are not necessarily representative. Indeed they almost certainly exaggerate the breeding success, leading to an estimate of 1.95 young reared per pair, against the 1.04 required to offset adult losses of 34%, if all Lapwings breed at 1 year old. Kraak, Rinkel & Hoogerheide (1940) report that some do not breed in their first year, in which case the requirement for replacement is somewhat higher. Lack (1943) arrived at a very similar theoretical production rate of 1.06 per pair.

RINGED PLOVER Charadrius hiaticula. Mortality. Though the British breeding stock, which is nearly sedentary, is somewhat

isolated from the Scandinavian stock, which migrates to S.W. Europe and N.W. Africa, there are no indications of differences in survival between them. The annual death-rate from the combined recoveries from ringing up to 1951 is 42.0 & 5.48% (calendar year grouping), in close agreement with the estimate of 41% arrived at by Laven (1940) from the study of a siIigle small colony. In recent years ringing in Sweden has preponderated. This has had the result of substantially increasing the apparent death-rate, the Swedish sample for the years 1951-57 showing losses of 55 & 10.4%. It is not clear whether the juveniles trapped in Sweden are drawn from a population with a higher death-rate or whether the rings used on these birds are being lost.

Fertility. The only intensive work on breeding success appears to be that of Laven (1940), a four-year study of a colony varying from 8 to 16 pairs. From the estimates of breeding stock and production, reinforcement by immigration must have occurred in at least one year, preventing direct measures of s1 and s for the colony. Attempts to calculate mortality rates from German breeding censuses given by Schulz (1947) are frustrated by the typically enormous fluctuations which were found. Sluiters (1954) has explained this instability of Ringed Plover populations in terms of their ecological requirements. In a species exploiting unstable habitats it is reasonable to expect relatively little tendency to remain in closed groups.

Details of the breeding success of Arctic-nesting Ringed Plovers would be of considerable interest. In the north the species is single-brooded and re-nests less freely than in the south. A few records in Johnsen (1953) suggest that fledging success in north Greenland may be higher than in Germany. In a group of 4 nests observed by Nordberg (1950) in the &and archipelago, Finland, in 1945, all 16 eggs hatched and 9 chicks were fledged.

LITTLE RINGED PLOVER Charadrius dubius. Mortality. The death-rate estimated from 15 recoveries is 43 & 13.8% (calendar year

grouping). If 8 recaptures in years after that of ringing are combined with the recoveries in a survival table (method after Hickey 1952), the apparent death-rate is reduced to 35+ 10.4%. Estimates with standard errors as large as these are, of course, not at all reliable and warrant inclusion only because of the interest attaching to comparisons between them and the death-rates of other species in the genus.

Bub (1958) studied a small group of one to five pairs over four years. More extensive records are diffused through the five papers by Parrinder (1950-60) describing the growth of the English population. The average number of young fledged by each English breeding pair is 2.22 when obtained as the product of the separate estimates of egg output, hatching and fledging, but only 1-55 from the records of young believed to have flown. The English breeding population between 1948 and 1959 grew in a remarkably steady way, with an annual rate of increase of 15.3%. This rate of increase can be used to check the estimate off, given s, or the other way about. For a species

Fertility.

VOL. 104 2A


breeding at 1 year old, the population increases or decreases in a geometrical progression according as (1 +f )s exceeds or falls short of unity (see Capildeo & Haldane 1954). A rate of increase of 15.3% corresponds to (1 + f )s= 1.153. For an adult death-rate of 35% this requires an output of 2.13 fledged young per pair, compared with the observed values of 2.22 to 1.55. Thus the data are consistent, within the wide limits set by their low precision. I t is quite likely that the English population was being increased by continued immigration. If so it could have been sustaining a rate of adult loss higher than 35%.

KENTISH PLOVER Charadrius alexandrinus. Mortality. Estimated adult death-rate from recoveries 40.0 & 10.3%. An analysis of

marking and recaptures of 108 full-grown birds at Amager, Denmark, in the years 1953-56 yields an estimate of 41&12.6%. About 55% of marked adults in a large German breeding colony returned one or more years after ringing (Rittinghaus 1956), indicating a death-rate of no more than 45%.

According to Rittinghaus (1 956) the Kentish Plover is. single-brooded, though it may re-nest if the first nest is lost. Lippens (1955) treats the species as double- brooded in Belgium, but the mean clutch-size there is less than 3, and in the Nether- lands it is 2.68 (Brouwer 1950). The colony on Oldeoog, studied for nine years by Rittinghaus, was decreasing, from over 90 pairs to under 60. From ringing it was clear that less than half the recruits to the breeding stock had been bred in the colony. It seems reasonable to assume that the immigrants came from colonies with similar output. The decrease in colony size, though not very steady, corresponded to an annual rate of 5.2%. Using the relationship (1 + f )s = 1 - 0 . 0 5 2 ~ 0.948 with s = 0.55 (from sight records and retrappings of ringed birds), f=0.727. If s, is roughly equal to s, as the recovery data suggest, the values of c, u and z1 obtained by .Rittinghaus lead to f = 3.0 x 0.94 x 0*50/2=0.705. The close agreement between these independent estimates of f is encouraging.

Fertility.

GOLDEN PLOVER Charadrius apricarius. Mortality. Few recoveries from ringing other than in Holland and Iceland. The

Dutch ringing of full-grown birds from Scandinavia and northwest Russia, caught on passage between October and March (up to 1957), represents a separate breeding stock from that of Iceland but the two death-rates are not statistically different. Despite the late capture dates of the Dutch birds and the probable mixture of adult with first-winter birds in the samples, the losses in the first year after marking (52.6%) are substantially higher than expected from the death-rate in subsequent years, suggesting that increased vulnerability extends beyond the first 1 January of life.

TURNSTONE Arenaria interpres. Mortality. The sample represents the Scandinavian and possibly the western Siberian

breeding population, not that from Greenland and eastern arctic Canada now believed to winter in western Europe. Most recoveries have been obtained in the year of ringing so that the number available for estimating the adult death-rate is small. The death-rate calculated from recoveries (33.6%) is considerably larger than that of 22.2% found by Bergman (1946) by a study of the return of marked adults to a breeding colony.

The index of first-year mortality for ringed nestlings is 42% ; for juveniles ringed in early autumn it is 56%. Since the juvenile sample is considerably the larger the true index seems likely to be closer to the second estimate. The lower value of the index from nestlings may well be due to undetected deaths between ringing and fledging.

Fertility. The discrepancy between the estimated death-rates is sufficient to require investigation. Bergman’s (1946) study leads to inconsistent statistics. The average

1962 HUGH BOYD : MORTALITY A N D FERTILITY OF CHARADRII 375

number of young fledged in the Finnish colony was 2.3 per breeding pair. If the first- year death-rate was 42% and that of adults was 22.2y0, and the birds matured at 2 years old, this output of young would have resulted in the breeding population increasing by 21.5% annually. If, on the other hand, the death-rates were increased to 56% in the first year and 33.6% subsequently, with the same output, the population would have been increasing by 0.35%. In fact, the population seemed to be nearly stationary at the time of Bergman’s observations. Nordberg’s data confirm that the output of fledged young is normally close to that reported by Bergman. Thus it seems likely that the high rate of survival of Bergman’s ringed breeding birds is unrepresentative of adults as a whole.

COMMON SNIPE Capella gallinago. British ringing was formerly of nestlings, but since 1950 full-grown birds of uncertain

origin have formed most of the reduced annual catch. The mean annual death-rate of those ringed up to 1958 was 48.3 k 5-65%, there being no marked differences between the rates before 1920 and those in each subsequent decade.

Though the scatter of the estimates from British and other sources is considerable, there is no statistical justification for regarding any as distinct. The weighted mean, 51.9 f 5.43y0, may be taken to represent the specific death-rate. There is no detectable difference between the survival of birds in the first year after fledging and that of oIder birds.

JACK SNIPE Lymnocryptes minimus. Only 22 recoveries are available for calculating the death-rate, which works out at

76 f 7.9%. It would be most surprising to find so high a figure confirmed by future work. No published recovery has been obtained more than 2$ years after marking and it seems likely that rings have been lost or become illegible, although ring wear does not seem to have been important in the case of the Common Snipe.

WOODCOCK Scolopax rusticola. Lack (1943) used 203 recoveries of Woodcock ringed in Britain up to 1930 to estimate

an adult death-rate of 37%. There was further intensive ringing up to 1939, but little thereafter. Nearly all British ringing has been of nestlings. For national ringing up to 1954, the adult death-rate is 40.7 2.26%. There is an interesting difference in the mean annual death-rates for the periods 1921-30 (34.3 f 3.48%) and 1931-40 (46.5+3-31%). Earlier ringing provides intermediate values : 44.3 & 3.48% from recoveries from ringing in a private scheme in Co. Sligo, Ireland, from 1910 onwards (data from Thomson 1929); 39.5 k 7.9% for birds marked under the ‘ British Birds ’ scheme up to 1920; and 37.7 f 10.2% for those marked privately in Northumberland between 1891 and 1908 (calculated with correction for incomplete recording from figures published by Percy 1909). The apparently increased death-rate in the period 1930-40 does not seem to be due to a falling- off in reporting after the outbreak of war in 1939, as might have been expected. There are indications that birds marked in some parts of the country (e.g. the Solway region) survived less well than those elsewhere, probably in consequence of differences in the pattern of local shooting: but it is clear that the differences in apparent death-rate between 1921-30 and 193 1-40 are not due to differences in the regional composition of the samples. The data are too few to permit useful estimation of changes in mortality from year to year.

The small-scale ringing on the continent of Woodcock bred around the Baltic, of which few appear to visit the British Isles, suggests the death-rate of these birds to be indistinguishable from that of our local birds. Too few ringed in Iceland and the Faroes have been recovered to enable separate estimates to be obtained for these breeding stocks.


CURLEW Numenius arquata. Though a large proportion of recoveries have been in the year of marking, it is

evident that Curlew are potentially long-lived: a Swedish-ringed bird was recently recovered in its thirty-second year. First year losses are about 62% and mortality in the second year of life also seems to be greater than in later years. Combining the British and overseas data, the death-rate in the second year is 33.0 f 4.39% ; in subsequent years it remains nearly constant at 25.2 f 2.50%. Recoveries of Curlew ringed since 1950 are too irregular to provide a satisfactory estimate of mean annual mortality but they confirm that losses in the second year tend to be higher than the average losses later.

WHIMBREL Numenius phaeopus. A very small sample, insufficient to provide a good index of first-year mortality and

quite inadequate for the exploration of relative losses in the second and later years of life.

BLACK-TAILED GODWIT Limosa limosa.

rate of loss in the first year after fledging and in later years. Mortality. Unusually, there is no appreciable difference between the apparent

Fertility. No detailed studies of breeding groups seem to have been published. Morley & Price (1956) showed that the British-wintering population increased considerably between 1938 and 1952. The breeding origins of these wintering birds are unknown but it seems plausible to argue (with Nsrrevang 1959) that they are chiefly Icelandic and perhaps also from Denmark and the Netherlands. If the origins of the British- wintering population remained unchanged during the period, the mean annual rate of increase, calculated from the annual maxima given by Morley & Price, might be taken to represent that of the northwestern breeding population. The estimate of the rate of increase so obtained is 124%. For a death-rate of 30.3% and breeding beginning at 2 years old (on the evidence of Dutch recaptures), this would require an annual output of 2.0 fledged young per breeding pair. Rough calculation from notes published about the output of the recently re-established and still very small breeding stock in England suggest an output of 1.64 (data from editorial notes in ‘ British Birds ’ 51 : 524-525 and ‘ Bird Notes ’ 28: 415-416, both 1958). The productivity of a peripheral breeding group seems quite likely to be lower than that of birds in long-established colonies.

BAR-TAILED GODWIT Limosa lapponicus. Apparent losses in the first year after marking amount to 79%, in strong contrast to

the finding for the Black-tailed Godwit, especially since the Bar-tails were ringed when full-grown rather than as nestlings.

WOOD SANDPIPER Tringa g2areola. Myhrberg (1961) in a study of the results of Swedish ringing decided that no estimate

of adult mortality was possible, apparentIy because of the preponderance of recoveries within a year of ringing and because of a difference in the proportion of casualties due to man in these first-year recoveries and those in later years (see Table 1). These objections do not seem decisive although they show that the index of first year mortality may be considerably exaggerated. Application of Haldane’s procedure to Myhrberg’s data (his Table 2, p. 140), omitting recoveries in the first year, leads to an estimate of 46-6 f 12.3°/0 for the aduit death-rate. A similar calculation using 34 recoveries from ringing in all countries up to 1956 leads to the result 46.4+ 10.2%. For juveniles ringed in July and August the index of first year mortality is 83-88y0.


COMMON SANDPIPER Tringa hypoleucos. Although a comparatively large number of recoveries is available, the adult recovery

series is a rather irregular one, not fitting the hypothesis of a constant death-rate very well, so that the true specific value is far from certain.

COMMON REDSHANK Tringa totanus. There are great differences in the apparent death-rates of the various

samples, from 17.7 to 56.9%. There are several reasons for supposing that the apparent rates for Danish- and British-ringed birds are too high, very probably because of ring loss. A capture-recapture analysis of ringing at Amager, Denmark, in the years 1953-56 indicates a death-rate of only 17.7 9.1%. This estimate is probably too low, because the published information on the number of birds ringed does not digerentiate between nestlings, juveniles and adults and in this species ringing at Amager probably includes a substantial proportion of young birds. But it suggests strongly that recaptured birds were apparently living longer. Redshank subject rings to unusually heavy wear. Replace- ment or adjustment of the rings prolongs the apparent life of birds with worn rings, as has been shown very plainly by ringing in England.

Grosskopf (1959) has used returns of ringed adult Redshank to a German breeding colony to show that the death-rate is not more than 30% (28.7 & 6.0%, calculated by the present writer from Grosskopf’s data). He argued also, from the rate of return in successive years, that the adult death-rate decreases with age: 30%, 23% and 18%. The argument is not conclusive, because the apparent increase in survival could also be due to an increasing tendency to return to the same breeding place with experience in breeding.

From examination of recovery data alone the best single value for the adult death-rate is probably that given by Swedish ringing, 3 1.5%.

Fertility. In Grosskopf’s (1958, 1959) three-year study of an expanding colony, he could not determine the numbers of young fledged although he notes that more than half the young hatched survive to fledging in favourable years : v = 0.5 has been used here. Grosskopf found that a small fraction of birds of known age begin to breed at one year, though the great majority do not begin until two. For the present purpose ihe assumption that all begin at two is accurate enough. Using the tabulated figures for breeding success and a death-rate of 29% applying to first-year and adult birds, the value off for the colony studied is about 0.82. If losses in the first year after fledging are greater than those in later years as the Swedish recoveries indicate, so that the first year mortality is 55%, f would become 0.52. These values may be compared-with the output required for a steady population, f=0*575. In fact the colony was increasing rapidly in size, though the number of breeding pairs in the third year of watching was not established. The recorded increase from 1955 to 1956 was from 55 to 75 breeding pairs (36%). For f = 0.82, and a death-rate of the expected steady rate of increase would be 9.2%. Presumablv substantial immigration was taking place.

Nordberg’s (1 950) records refer to only a small colony and cover rearing success in only a single year, but they provide useful confirmation of the German results.

KNOT Calidris minuta. Fertility. Notes by Parmelee & Macdonald (1960) on a group of nine nests in West

Ellesmere Island provide the only quantitative data on breeding success. The age at which Knots first breed is unknown. If they are mature at one year, a steady population with an adult death-rate of 32.4% and producing 1.66 fledged young per pair would require a first-year mortality index of about 61%. If maturity is not reached until two years old, as seems likely from the abundance of non-breeders in summer south of the nesting range, the corresponding index of first-year mortality would have to fall to 42% for the population to remain in equilibrium. If the first-year mortalitv index were

Mortality.


really as high as 81% with adult mortality 32.4y0, the output of fledged young per breeding female would have to be increased to 3.42, if the species matures a t one year (or 5.05 if maturity is delayed until two). Such an output seems most unlikely and it seems proper to reject the first year mortality index given by the recoveries. Presumably it is seriously biased by the differences in vulnerability to shooting between young and older birds which are suggested by Table 1.

DUNLIN Calidris alpina. Martin-Lof (1961) has estimated the adult mortality from Swedish data at 38.9 & 3.6%.

Calculations made for this survey from unpublished Swedish recoveries give a rather lower figure but the difference is not statistically significant and Martin-Lof’s value is used here. The mean death-rate in 1948-54 from the three Scandinavian sources combined is 37.7 f 3.60%.

Martin-Lof puts the apparent losses of Swedish-ringed juvenile Dunlin in their first year at 62%. The Norwegian sample includes few age-classified birds : from the Danish recoveries the first year mortality index of juveniles is of the order of 75%.

In view of the known differences in the breeding and wintering distribution of various elements among Scandinavian-ringed Dunlin (Nsrrevang 1955) it is of interest to see whether any differences in apparent death-rates can be found by grouping the recoveries according to the country of death. The results are entirely negative, despite the seemingly great differences in ‘‘ hunting pressure ” experienced by birds wintering, for example, in France and in England. Following up the study at Ottenby in 1957 (Martin-Lof 1958), which revealed size differences between early and late migrant young Dunlin, indicative of two populations of different origin, three recovery series have been assembled for Swedish-caught juveniles : from those marked in July/August (early migrating stock), those marked in the second half of September (late migrants) and the mixed group taken in the first half of September. These series fail to give any indication that the mortality of the stocks may differ.

CURLEW SANDPIPER Calidris testacea. The recovery series is too small and erratic to provide more than a very doubtful

guide to the mortality rates of this species, ringed on passage from its north Siberian breeding grounds.

SANDERLING Crocethia alba. Ringed on a useful scale only in Norway as passage migrants from Siberia and Green-

land. Though the recovery series is little bigger than that for the Curlew Sandpiper, it is more consistent and may give a reasonable approximation to the true death-rate.

RUFF Philomachus pugnax. Ringed in nine countries, with most recoveries from Swedish, Dutch and Danish

ringing. Recoveries from ringing up to 1954 give a death-rate of 47.6k 3-61%, with no difference in the rate of loss between the first and later years of life, despite the considerable discrepancy in the proportion killed by man suggested by Table 1. There is very close agreement between estimates from regional samples.

This is the only species in which most captured birds have been classified by sex but the samples are too small to justify the assertion that a real difference exists in the mortality- rate of the two sexes: among 42 recoveries of known males the death-rate is 50.0 * 5*45%, while the death-rate of 13 recovered females is 40.6 & 8.68%.

Recent marking in Finland and Great Britain is not used here.


AVOCET Recurvirostra avosetta. There is no evidence of regional differences in survival, but there are

indications that losses in the fourth and fifth years may be higher than in the second and third (44-52%, compared with 33%). The reason for such a difference in mortality with age is not obvious, though if Avocets begin to breed at three years old it may reflect a period of comparative security in the pre-breeding stages.

Fertility. No intensive study of the breeding success of a group of Avocets in one of the strongholds of the species seems to have been published. The richest source of information is the series of reports on the growth and welfare of the recently re-established colony in Suffolk, published each year since 1948 by the Royal Society for the Protection of Birds, in ' Bird Notes ' or in its Annual Reports. The numbers of young hatched each year were known and in most years the numbers of young flying were also estimated with some confidence, though in the peak years this became very difficult. Hatching and fledging success varied very considerably. The age at maturity is either 2 or 3: a recapture in Germany of a breeding bird marked three years previously as a nestling (Bub 1961) is the only positive evidence. If the Continental estimates of death-rates of 38.4% for adults and 64% in the first year are taken with the average values for the Suffolk stock of 69% for hatching success and 38% of hatched young fledged, the expected rate of change of the population would be - 17.2% assuming breeding at 3, or - 11.6% if breeding begins at 2. The Suffolk population was in fact increasing greatly over the period, at a nearly uniform rate of 22.3% in the years 1949 to 1957. If it is supposed that the average output of fledged young has been correctly assessed at 1.11 per pair, the discrepancy between observation and expectation must mean either that the mortality of Suffolk adults was much less than that of Continental birds or that the breeding stock was being reinforced by immigrants from elsewhere. If immigration was not occurring, the annual mortality of adults in the years 1950-57 must have been only about 9% if Avocets breed at 3, or 15% if they breed at 2. Since the adults leave the protected area where they nest for most of the year such low rates of loss are unlikely and continued immigration seems a more probable explanation of the increasing breeding stock.

In 1959-61 the breeding population was nearly steady at about 65 pairs and breeding success was low, about 44,35 and 65 fledged young in the three years. If the levelling-out, apparently due to ecological limitations, is assumed to have ended immigration, with losses of breeding birds being made good by the entry of locally-bred young, the gross annual mortality of adults in those years must have been about 24%, still well below the expected rate for Continental birds.

Though no estimates of local production are available, it is of some interest to look at changes in a colony on the Hamburger Hallig, on the German North Sea coast, in the years 1927-47. During most of the period the colony was increasing, at a mean annual rate of 8.3%. Using the Continental estimates of death-rate, this rate of increase would have required an average output of 7.3 fledged young per pair for breeding at 3 years old, or 4.24 for breeding at 2. Even in the best year of the SufTolk colony (1952) the output of fledged young per pair was only 2.5. Again it seems necessary to assume either that adult losses were reduced to no more than 29%, instead of 38*4%, or that an excess of immigration was occurring.

Mortality.

MORTALITY, FERTILITY AND TAXONOMIC RELATIONSHIPS

The statistics presented here suggest that the adult mortality-rate may serve as a parameter of each specific population. The evidence indicates that the death-rates of different stocks within a species tend to similar values, providing that the stocks are in a nearly steady state. Multiple estimates for different stocks within eleven species show such agreement. Only for two species, the Oystercatcher and Redshank, is there serious

3 80 HUGH BOYD : MORTALITY AND FERTILITY OF CHARADRII IBIS 104

conflict between estimates. In both it seems more likely that the discrepancies are due to demonstrable ring failures than to differences in the life-tables of the birds themselves.

In the family Anatidae, Boyd (1962) found evidence of the existence of specific mortality-rates and showed also that closely related species had closely similar death-rates. Table 2 lists specific rates for 22 of the species considered in this paper, the rate for the Jack Snipe being rejected. The rates given for those species for which several estimates have been given earlier in the text are means of those estimates believed to refer to steady populations and to be little biased by such factors as ring loss or failure to " home ". The adjusted means have been calculated by weighting each individual estimate with its variance.

TABLE 2. Adult death-rate, average wing-length and body-weight of European wading birds (Charadrii), together with the cube-root of the body weight. Only the values for those species marked with an asterisk have been used in estimating regression coefficients.

"Oystercatcher

"Lapwing

"Ringed PIover

Haematopus ostralegus

Vanellus vanellus

Charadrius hiaticula Little Ringed Plover

C . dubius Kentish Plover

C . alexandrinus "Golden Plover

C . apricarius

Arenaria interpres

Capella gallinago

Scolopax rusticola

Numenius arquata

N . phaeopus *Black-tailed Godwit

Limosa limosa Bar-tailed Godwit

L. lapponica Wood Sandpiper

Tringa glareola Common Sandpiper T. hypoleucos

Redshank T . totanus

Calidris minuta

C. alpina

C. testacea

Crocethia alba

Philomachus pugnax

Recurvirostra avosetta

Tumstone

*Snipe

*Woodcock

*Curlew

Whimbrel

"Knot

"Dunlin

Curlew Sandpiper

Sanderling

*Ruff

*Avocet

Adult death-rate

d ( % ) 15.7

34.3

42.0

35.0

40.5

40.7

33.6

51.9

41.3

25.2

30.8

30.3

39.5

46.4

48.4

31.5

32.4

37.7

33.0

44.0

47.6

38.4

Wing-length

w (-.I 261

226

133

116

113

188

153

134

196

3 00

248

222

214

125

112

157

168

113

130

125

175

225

Body weight

M (m.1 500

200

55

38

46

200

100

130

280

700

550

290

270

61

60

130

109

51

55

48

156

360

(Weight)'I3

m 7.94

5.85

3.80

3.36

3.58

5.85

4.64

5.07

6.54

8.88

8.19

6.62

6.46

3.94

3.91

5.07

4.78

3.71

3.80

3.63

5.38

7.11


l n the Anatidae, a single family, the range of death-rates in 23 species was 14% to 52% (Boyd 1962) compared with 15.7% to 51.9% in the 22 Charadrii considered here. The similarity of these ranges is presumably accidental. The point to be made is that a taxonomic Family is not a very homogeneous assemblage, so that the wide range of death- rates in the 14 species of Scolopacidae (25.2-5 1.9%) is not necessarily inconsistent with the hypothesis of similarity, although the range 3 4 4 3 % for the 6 species of Charadriidae is much narrower.

I t is obvious from Table 2 that few comparisons between members of a genus are possible. One genus, Charadrius, is represented by four species and two others, Tringa and Calidris, by three. All three estimates for Tringa, two for Charadrius and one for Calidris are of low reliability. The values for Charadrius and Calidris are closely grouped and consistent with the hypothesis that nearly related species have similar death-rates. In Tringa the Redshank rate appears very different from those of the other two species.

The assertion that species in equilibrium have characteristic death-rates is equivalent to saying that their effective fertility is specific. The study of fertility in birds is still in an undeveloped state. The most powerful line of inquiry has been through the investigation of clutch-size (Lack 1954). This is unrewarding in the case of waders, in which most Palaearctic species have a modal clutch of four. The four species of Charadrius discussed here provide a striking illustration of diversity in egg production, varying between an average of over 6.3 eggs per breeding female in southern populations of the Ringed Plover, often double-brooded and re-nesting readily, and the low output of the single-brooded Kentish Plover with a typical clutch of three. Yet despite these variations in output the rate of entry of young birds into the breeding population appears to be very much the same. Analogous examples occur in the Anatidae, notably in the diving ducks Aythya. In groups such as these it seems to be more fruitful to think in terms of recruitment to the breeding stock than to attempt to use a “birth-rate” as a population parameter.

MORTALITY AND BODY-SIZE

Table 2 gives the impression that larger waders have lower death-rates than smaller ones. This is in agreement with a general tendency in vertebrates, which led Bourlihe (1946) to the hypothesis that potential longevity is a direct function of size. Further examination of this relationship is of interest from two points of view. Of primary importance, there are the general problems of the factors determining mortality and fertility. A discussion of these fundamental questions will not be attempted here, as it must involve drawing on material outside the scope of this review.

The second approach is a purely empirical one: can a simple relationship between survival and body-size be demonstrated and what use can be made of it? No sufficient single measure of body-size is obtainable, but it has been found that wing-length and total weight provide useful indices. For the present purpose it has been necessary to arrive at a single specific value for each of these measures, despite the variation to which they are subject. This has meant neglecting differences between the sexes (females tend to be larger than males), changes in average measurements between subspecies or stocks in different parts of the specific range, seasonal changes in weight and other such complications. Since high precision is unattainable, a crude estimate of the mean wing-length of each species has been obtained by taking the mean of the mid-points of the ranges for males and females given in Witherby et al. (1940). Records of weights have been assembled from a variety of sources, principally Heinroth (1922) and Dementiev & Gladkov (1951). The figure used has most often been a mean obtained from the data in the latter work. Table 2 records the figures for average wing-length and weight, and the cube root of the weight, as well as the adult death-rates. The cube root of the weight is the most appropriate index to compare with linear measurements, weight being proportional to volume and so to the product of three linear dimensions (Amadon 1943).

HUGH BOYD : MORTALITY AND FERTILITY OF CHARADRII IBIS 104 382

There is a very strong positive correlation between wing-length (w) and the cube-root of body weight (m) and the scatter of the observed values around the regression line is small enough to suggest that the use of either measure as an index of size should lead to similar results.

The regression line d=61.09-4.147 m was obtained by the least squares method applied to the values of d (the adult death-rate) and m (the cube root of body weight) for the twelve species marked with an asterisk in Table 2, these being species for which the standard error of the estimate was less than one-sixth of the death-rate.

By a similar calculation, the regression of death-rate on wing-length is described by the equation d=61*26-0.127 w, again with broad limits of error. A point of interest here is the resemblance between the hypothetical values of the two equations when m=w=O, when d equals 61.09 or 61.26 respectively. In practice the lowest known values for members of the Charadrii are about m=2.75 and w=90, but the limiting values serve to suggest that death-rates of over 60% are unlikely to be found in steady populations of any species of wader. The reason for this probably lies in the practicable rate of recruitment. With an annual loss of 60% of adults it would be necessary for at least three young per mature pair to be fledged successfully. The studies reviewed earlier show that such a level of production is most unlikely to be maintained over any long period even by Charadrius.

With improved measures not only of the death-rate but of body-size it might be possible to estimate correlations with substantially greater precision. If this could be done it should be possible to predict within useful limits the appropriate value of the death-rate for a species of known body-size. The difficulties in the way of such prediction are considerable but it may well be easier to obtain adequate measurement data than to estimate mortality directly for species breeding, for example, in Arctic Siberia or in Africa.

SUGGESTIONS FOR FURTHER INVESTIGATIONS

The most fruitful approach to the dynamics of wader populations seems to be by concentration on long-term observations of breeding groups. The especial need is for careful breeding censuses, including determinations of the numbers of young fledged, coupled with marking to deal with the problems of emigration and immigration and the age of maturity. Such investigations might well be made at bird observatories, as has been done at Skckholm, though the range of species available is small.

For Arctic-breeding species, long-term nesting studies are almost certainly impracticable and at present little can be done to fill the gap by observation and ringing on passage or in winter-quarters. The existing evidence suggests that differential immigration of adults and juveniles will create great difficulties in estimating annual production by sampling of passage birds. Moreover, much has still to be done to improve the classification by age and sex of waders caught for ringing. The-value of most of the ringing of full-grown waders done so far has been greatly reduced by the poverty of the data recorded. In species such as waders for which cumulative recovery rates are only of the order 1 4 % it is very necessary to extract as much information as possible from the birds at the time of marking. The determination of sex will not be easy. Recent investigations have shown that even in species for which marked sexual dimorphism in size has been recorded in taxonomic work (e.g. Curlew, Black-tailed Godwit) the amount of overlap found in large captured samples is inconveniently great. Partial segregation of juveniles from older birds present in the same area, which has recently been found in Dunlin flocks, threatens further complications. Yet it is particularly desirable to discover whether the mortality experience of males and females differs significantly and what the sex-ratios in different age-classes and regional groups may be.


From the point of view of conservation, which continues to increase in urgency, tha most important feature of what is now known about the dynamics of wading birds is the difference between the species with high fertility and mortality and those with a lower population turnover. There is a lack of flexibility inherent in the dynamics of slow- maturing species of low fertility which renders them particularly vulnerable to any increase in mortality of full-grown individuals. Breeding populations of small-sized waders, such as the ringed plovers, fluctuate widely and erratically, those of larger species more slowly. In the case of the small birds it is easy to get alarmed too soon, in that of the large ones too difficult to raise the alarm soon enough. If measures of conservation are to gain support, it is essential that much more should be learned about the inherent characteristics of wader populations, so that the likely outcome of proposed changes in legislation of land use can be predicted correctly more often than not.

SUMMARY A review of published data on the mortality and fertility of 23 species of wading birds

(Charadrii) breeding in or visiting western Europe. Recoveries of ringed birds are the main source of estimates of mortality. In some cases

recaptures of marked birds can also be employed. Apparent mortality in the first year after fledging is usually higher than in later years, though most estimates are probably biased by the preponderance of recoveries due to shooting. Adult mortality-rates in stable populations vary from about 15-7 % (Oystercatcher) to 51.9 % (Common Snipe) with most in the range 30-45 %. Closely related species tend to have similar mortality-rates. There is a strong inverse correlation between death-rate and body-size, using wing-length and weight as indices of size.

Few waders are double-brooded, though many re-nest if their first nest is destroyed. In most thriving breeding colonies, 66-96% of the eggs laid hatch. Survival of chicks from hatching to fledging, which is hard to measure, typically averages 40-80%, though success often varies widely from year to year.

Intensive long-term studies of breeding groups make the most effective contribution to knowledge of population dynamics. For the many species for which breeding studies are likely to remain impracticable, studies of population composition in winter or on passage may provide useful substitutes, but only if techniques of sampling and of age- and sex-classification can be improved.

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Tidsskr. 49 : 18-49.

results. Vidensk. Medd. Dansk Naturh. Foren. Kbh. 121 : 181-222.

adjacent areas. Nat. Mus. Canada Bull. 169 : 1-101.

Birds 43:279-284 ; 45: 61-64 ; 47:198-203 ; 50: 365-371 ; 53: 545-553.

Rylens (Calidris alpina (L.) ) trek i Nordeuropa.

Woodcock marked at Alnwick. Country Life : 323. Uber die Verhalten eines von Sandregenpfeifer (Charadrius hiaticula)

ausgebruteten und gefuhrten Seeregenpfeifers (Ch. alexandrinus). Vogelwarte 15 : 187-192. Untersuchungen am Seeregenpfeifer (Charadrius alexandrinus L.) auf

der Insel Oldeoog. J. Om. 97 : 117-155.

Observations on the Kentish, Little Ringed and Ringed Plover, breeding

The migration of British and Irish Woodcock : results of the marking

Some observations and breeding records of the Lapwing, Skokholm, 1952.

North-western

The Handbook

Limosa 27 : 71-86.

Brit. Birds 22 : 74-92.

London : Witherby. H. Boyd, The Wildfowl Trust, Slimbridge, Glos.

APP

EN

DIX

M

orta

lity

and

fer

tili

ty s

tati

stic

s of

E

urop

ean

Cha

radr

ii,

deri

ved

from

pub

lish

ed r

ecov

erie

s of

rin

ged

bird

s (s

uppl

emen

ted

by u

npub

lish

ed B

ritis

h re

cord

s) a

nd p

ublis

hed

All

calc

ulat

ions

are

by

the

wri

ter,

exc

ept

whe

re s

tate:.

Fi

gure

s in

par

enth

eses

are

esp

ecia

lly u

ncer

tain

, an

d th

ose

in s

quar

e br

acke

ts a

re r

ejec

ted

as m

isle

adin

g, f

or

Mea

ning

of

colu

mn

head

ings

in

Fer

tili

ty s

ecti

on:

c=m

ean

num

ber

of

eggs

lai

d pe

r fe

mal

e pe

r ye

ar;

u=fr

acti

on

of

eggs

lai

d w

hich

ha

tch;

v=

frac

tion

of

ha

tche

d

wor

k on

bre

edin

g su

cces

s.

reas

ons

disc

usse

d in

the

tex

t.

All

esti

mat

es i

n co

lum

n

youn

g w

hich

fly

; a=

age

at s

exua

l m

atur

ity

(in

year

s).

G.B

. =G

reat

B

rita

in.

1st

year

mor

tali

ty

"are

to

be t

reat

ed w

ith

rese

rve.

Fur

ther

exp

lana

tion

in't

ext.

MO

RT

AL

ITY

n

,

n,

70 70

Rec

over

ies

Ann

ual

1st y

ear

Spec

ies

Rin

ging

sou

rce

used

to

tal

mor

tali

ty

mor

tali

ty

Not

es

Oys

terc

atch

er

Hae

mat

opus

ost

rale

gus

Lap

win

g V

anel

lus v

anel

lus

Rin

ged

-Plo

ver

Cha

radr

ius h

iatic

ula

Lit

tle

Rin

ged

Plov

er

Cha

radr

ius d

ubiu

s

Ken

tish

Plo

ver

Cha

radr

ius a

lexa

ndri

nus

Hol

land

192

5-50

G

.B.

1909

-58

Den

mar

k 19

20-4

6 Sw

eden

}t

o 19

54

Nor

way

M

ellu

m,

Ger

man

v 19

49-5

3

G.B

. to

195

2 G

.B.

to 1

950

Swed

en

7 D

enm

ark

othe

r co

untr

ies

Ger

man

y 19

36-3

9

Swed

en 1

951-

57

7 co

untr

ies

to 1

956

Ger

man

y

othe

rs

Am

ager

, Den

mar

k,

Old

eoog

, Ger

man

y 19

53-5

6

138 71

25

31

143

728 46

48

18

12

10 7 33

23

18 5

108

246

15.9

k 1.

45

36

282

29.0

k9.4

82

26

.2k4

.8

62

30.0

23.7

14

.0 f 4.

3

34.3

f 1

.06

42

51

55.0

+10.

4 58

35

.0f1

0.8

53

iy 1 4

0.0f

10.3

47

I J

41.0

+ 12

.6

45

Gre

at m

ajor

ity r

inge

d as

f

iEii

ng

. cal

enda

r-ye

ar

Cap

ture

-rec

aptu

re

of

bree

ding

adu

lts

: da

ta

from

Jun

gfer

(19

54).

Cal

cula

ted

by

Hal

dane

(1

955)

.

Cal

enda

r-ye

ar

grou

ping

ba

sed

on r

ingi

ng u

p to

19

51.

Bri

tish

ri

nged

m

ostl

yas

pull

i, Sc

andi

- n

avid

mos

tly a

s juv

en-

ile,

G

erm

an

prob

ably

m

ostlv

as

mat

ure.

Ca

lculat

ed

by

Lav

en

(1 94

0).

Mar

ked

as p

ulli

: ca

len-

da

r-ye

ar

grou

ping

, in

- cl

udin

g re

capt

ures

.

Mos

tly m

arke

d as

pul

li :

cale

ndar

-yea

r gro

upin

g,

incl

udin

g re

capt

ures

. C

aptu

re-r

ecap

ture

.

Cal

cula

ted

by R

itti

ngha

us

(195

6) f

rom

rec

aptu

res

of b

reed

ing

bird

s.

FER

TIL

ITY

cu

va

So

urce

2.67

0.

66

0.75

3.

01

0.79

0.

046

2.88

0.

92

0.78

4.75

0.

52

8.50

00

48

0.67

4.

34

0.70

0.

64

6.3

0.36

0.

46

4-8

0.70

5-46

0.

55

0.74

3.0

0.94

0.

50

Skok

holm

(K

eigh

ley

1949

) N

orde

roog

(Dir

ckse

n 19

32)

ha

nd

(N

ordb

erg

1950

)

Skok

holm

(V

erno

n 19

53)

Ger

man

y (L

aven

194

1)

Switz

erla

nd (

Glu

tz 1

959)

G

erm

any

1936

-39

(Lav

en 1

940)

Ger

man

y 19

48-5

1

Eng

land

(Pa

rrin

der

1950

-

Old

eoog

(Rit

ting

haus

195

6)

(Bub

195

8)

60)

MO

RT

AL

ITY

%

%

Rec

over

ies

Ann

ual

1st y

ear

Spec

ies

Rin

ging

sou

rce

used

to

tal

mor

talit

y m

orta

lity

Not

es

Gol

den

Plov

er

Chu

radr

ius

apri

cari

us

Tur

ns to

ne

Are

nari

a in

terp

res

Com

mon

Sni

pe

Cup

ella

gal

linag

o

Jack

Sni

pe

Lym

nocr

ypte

s m

inim

us

Woo

dcoc

k Sc

olop

ax r

ustic

ola

Cur

lew

N

umen

ius

arqu

ata

Whi

mbr

el

Num

eniu

s pha

eopu

s

Bla

ck-t

aile

d G

odw

it Li

mos

a lim

osa

Bar

-tai

led

God

wit

Lim

osa

lapp

onic

a W

ood

Sand

pipe

r Tr

inga

gla

reol

a

Hol

land

to

1957

Icel

and

1933

-50

Nor

way

Sw

eden

]t

o 1

954

Finl

and

J Fi

nlan

d

G.B

. to

1958

Sc

andi

navi

a to

195

5 B

elgi

um 1

Ck

m;y

j'to

19

57

Icel

and

to 1

951

123

241

39.0

k5.4

2

31

64

46.5

k10.

3

'f :?

} 33.

6k3.

95

11

30

22.2

184

195

48.3

k5.6

5 60

70

56

.1k4

.80

184

195

48.3

k5.6

5 60

70

56

.1k4

.80

17

22 j

19

37

51

-4k8

-2

Bel

gium

, D

enm

ark,

3 E

ngla

nd &

Ger

man

y )

22

[76*

0 k 7.9

1 to

195

5 J

G.B

. & Ir

elan

d 18

91-

251

485

40.7

2-

26

Bal

tic c

ount

ries

up

to

29

55

43.9

k6.

11

'!; 2g:

} 25.

2+2-

50

G.B

. Sw

eden

]to

19

50

othe

rs

J 17

20

5

1954

1953

othe

rs

Icel

and

}to

1951

if }

30.8

k9.1

iz !:

} 30.3

k3.

2 ot

hers

10

16

othe

rs

}to

1956

Swed

en

27

103

Den

mar

k }t

o 19

56 }

Finl

and

31 } 46

.4f1

0-2

53

66

42-5

5

Au

tw-c

aug

ht

full

grow

n :

year

s fr

om

mar

king

, om

itti

ng 1

st.

Nes

tling

s an

d ju

veni

les :

cale

ndar

- yea

r gro

upin

g.

Finn

ish

larg

ely

pulli

, ot

hers

juve

nile

: c

alen

- da

r-ye

ar g

roup

ing.

R

ecap

ture

s of

br

eedi

ng

adul

ts (

Ber

gman

194

6).

Yea

rs f

rom

mar

king

, in

- cl

udin

g 1s

t yea

r.

Yea

rs f

rom

mar

king

, ex

-

Cal

enda

r-ye

ar g

roup

ing.

Pulli

, yea

rs fr

om m

arki

ng,

clud

ing

1st y

ear.

afte

r fi

rst

2 ye

ars.

Pulli

and

pas

sage

mig

rant

s :

both

gro

ups

by

year

s fr

om m

arki

ng.

Pulli

, yea

rs fr

om m

arki

ng.

Pass

age-

mig

rant

s :

cale

n-

Pass

age-

mig

rant

s :

cale

n-

dar-

year

gro

upin

g.

dar-

year

gro

upin

g.

FE

RT

ILIT

Y

C u

va

So

urce

3.8

4.0

4.0

4-0

3.8

3.84

3-7

0.83

0.72

0.

81

0.85

0.

73

0.78

0.74

0.89

0.77

Faer

oes

(Will

iam

son

1946

)

Icel

andi

c re

capt

ure

Finl

and

(Ber

gman

194

6)

Finl

and

(Nor

dber

g 19

50)

Elle

smer

e Is

land

(Pa

rmel

ee

& M

acdo

nald

196

0)

Faer

oes

(Will

iam

son

1946

) Ic

elan

d re

cove

ry

1 B

ritis

h Is

les

(Ale

xand

er

1945

-47)

Faer

oes

(Will

iam

son

1946

)

(1, 2

) H

unga

rian

& D

utch

reca

p-

ture

s.

1 Sw

edis

h re

cove

ry

MO

RT

AL

ITY

n

, 0

,

70

70 R

ecov

erie

s A

nnua

l 1s

t yea

r Sp

ecie

s R

ingi

ng s

ourc

e us

ed

tota

l m

orta

lity

mor

talit

y N

otes

Com

mon

San

dpip

er

Trin

ga h

ypol

euco

s

Com

mon

Red

shan

k Tringa to

tanu

s

Kno

t C

alid

ris

min

uta

Dun

lin

Cal

idri

s al

pina

Cur

lew

San

dpip

er

Cal

idri

s te

stac

ea

Sand

erlin

g

Ruf

f Cro

ceth

ia a

lba

Philo

mac

hus p

ugna

x

Avo

cet

Rec

urvi

rost

ra a

vose

tta

Swed

en

Den

mar

k ot

hers

G

.B.

to 1

958

Swed

en to

195

8 ot

hers

to 1

953

Den

mar

k to

195

6 A

mag

er,

Den

mar

k,

Ger

man

y 19

53-5

6

Swed

en

to 1

954

Nor

way

othe

rs

Swed

en 1

948-

58

I N

orw

ay 1

946-

57

Den

mar

k 19

51-5

6

Swed

en

Den

mar

k) 1

946

to

Nor

way

J

1957

N

orw

ay 1

939-

52

Swed

en 1 ?

to 1

954

othe

rs

~ j

Den

mar

k H

olla

nd

Bel

gium

Sw

eden

21

36

9 25

8

35

7 24

8

16

67

160

55

124

18

53

121

189

112

(48-

4 f 8-

34)

[41*

2 7.

01

31.5

6.7

[4

0*9 f 7-

41

[56.

9 7.

0)

[17.

7 &

9-11

28.7

f 6.

0

10

11 a

317

38.9

f3.6

60

247

34-O

f6.6

2 54

12

2 28

.6k1

2.4

14

31 1 (33

-Of1

3-3)

21

38

44.0

k11.

3

39

62 1

i! )- 47

.6k3

.61

26

27

54

120 1

79

55

[811

62

75

71

62

48

64

Mos

tly p

assa

ge-m

igra

nts :

cale

ndar

-yea

r gro

upin

g.

Nea

rly

all p

ulli

or ju

ven-

ile

s :

cale

ndar

-yea

r gr

oupi

ng.

Cap

ture

-rec

aptu

re

of

pass

age

mig

rant

s.

From

re

capt

ures

at

a

bree

ding

col

ony

(Gro

ssko

pf 1

959)

.

dar-

year

gro

upin

g.

Pass

age

mig

rant

s :

cale

n-

Cal

cula

ted

by M

artin

-Lof

(1

961)

. A

ll 3

sam

ples

w

ere

of

bird

s on

pas

sage

: yea

rs

from

mar

king

. Pa

ssag

e-m

igra

nts :

cale

n-

dar-

year

gro

upin

g.

Pass

age-

mig

rant

s :

cale

n-

Pulli

or j

uven

iles :

year

s da

r-ye

ar g

roup

ing.

from

mar

king

.

P+li

: ye

ars

from

mar

k-

ing.

F~

TIL

ITY

CU

VU

So

urce

4-0

3.8

4-0

4.0

3.73

4.2

0.8

Eng

land

(C

uthb

erts

on

et

al. 1

952)

1

Nor

weg

ian

reca

ptur

e,

. Fi

nnis

h re

cove

ry

0.86

(0.5)

mos

t G

erm

any

(Gro

ssko

pf 1

958,

2,

a

1959

) fe

w 1

09

6 0.

41

Finl

and

(Nor

dber

g 19

50)

0.83

0.

5

0.64

0.69

0.

38

Elle

smer

e Isl

and

(Par

mel

ee

& M

acdo

nald

196

0)

1 D

enm

ark

(And

erso

n 19

44)

Suff

olk,

Eng

land

(R

.S.P

.B.

1948

-61)

(3)

Ger

man

rec

aptu

re

mortality and fertility of european charadrii

Documents