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ORNITOLOGIA NEOTROPICAL 17: 333–352, 2006© The Neotropical Ornithological Society

BIRDS OF THE SIBUN RIVERINE FOREST, BELIZE

Victoria D. Piaskowski1, Mario Teul2, Kari M. Williams1, & Reynold N. Cal2

1Birds Without Borders – Aves Sin Fronteras®, Zoological Society of Milwaukee, 1421 North Water Street, Milwaukee, Wisconsin 53202, USA. E-mail: [email protected].

2Birds Without Borders – Aves Sin Fronteras®, Foundation for Wildlife Conservation, Inc., P.O. Box 97, Belmopan City, Cayo District, Belize.

Resumen. – Aves de la selva de galería del Río Sibun, Belice. – Con el fin de contribuir al conocimientosobre las especies de aves de las selvas de galería, conducimos inventarios durante 39 días entre 2000 y2003 en un área de 20 ha de selva a lo largo del Rió Sibun en Belice central. Las especies presentes fuerondetectadas usando redes de neblina, censos diarios de 2 h y observaciones casuales. Detectamos un total de196 especies de aves, de las cuales 151 fueron residentes permanentes, 38 migratorias y/o de paso, 4 resi-dentes estaciónales y 3 residentes/migratorias Neotropicales. Del total, 79 especies fueron consideradascomunes en el sitio, 39 poco comunes y 78 raras. Identificamos 19 especies amenazadas y 5 especies endé-micas en sus ámbitos. El estudio del hábitat ribereño provee datos fundamentales sobre las especies pre-sentes en este tipo de selva, libres de impactos humanos, y contribuye a la información disponible sobre laavifauna que utilizan tales hábitat en Belice durante la época no reproductiva.

Abstract. – An inventory of the bird species was conducted on 39 days from 2000 to 2003 in a 20-ha studyarea in riverine forest along the Sibun River in central Belize. Bird species present were detected throughmist-netting, a 2-h daily census period, and casual observations. We detected a total of 196 bird species, ofwhich 151 were permanent residents, 38 were migrants and/or transients, 4 were seasonal residents, and 3were resident/migrants. Seventy-nine species were considered common at the site, 39 were uncommonand 78 were rare. Nineteen species of conservation concern and five restricted-range endemics were iden-tified at the site. This study provides baseline data on the bird species present in an area of riverine forestnot disturbed by humans and contributes to the information available on the avian species utilizing ripar-ian habitats in Belize during the non-breeding season. Accepted 17 January 2006.

Key words: Birds, riverine forest, census, mist-netting, Belize.

INTRODUCTION habitats in South America and found them to

Riparian habitats have been shown to beimportant in maintaining biodiversity(Naiman et al. 1993). Studies of the bird com-munities present in riparian areas conductedin North America (Knopf et al. 1994, Darveauet al. 1995) have shown riparian habitats to behigh in bird species richness. Lovejoy (1974),Remsen & Parker (1983), and Terborgh et al.(1990) conducted detailed studies in riparian

be sites of high bird species diversity andabundance. Hutto (1980) studied bird use of13 habitats in western Mexico from Januaryto March and found that the greatest numberof species was present in riparian gallery andsecond growth forests. However, the riparianforest he studied bordered cultivated fields.Morton (1980) studied migrant use of 14habitats including a riverine forest fromDecember to March in the Panama Canal

333

PIASKOWSKI ET AL.

Zone and found that migrants concentratedin riverine forest relative to upland forest onthe Pacific slope. Studies describing the birdspecies composition of riparian areas wereconducted in undisturbed areas of southernBelize by Brokaw & Lloyd-Evans (1987)and Mallory (1991). Both described riparianareas as being high in bird species richness.Mallory et al. (2004) conducted mist-netting inforests in northwestern Belize (Rio BravoConservation and Management Area) andfound that the number of species captured inriparian and palm forest were significantlyhigher than in upland forest sites. To add tothe knowledge of the avifauna utilizing ripar-ian areas in Belize and to provide baselinedata for an area that is subject to continuingdevelopment pressure (Boles 1999), we con-ducted research from 2000 to 2003 in an areaof riverine forest along the Sibun River thathad no evidence of recent human distur-bance.

Little published information is availableon the bird species composition of riparianforests in central Belize. Ornithological stud-ies contributing to the knowledge of the avi-fauna of Belize have been conducted theresince 1857 (Russell 1964). Russell (1964) con-ducted field studies during 13 months in Brit-ish Honduras (now Belize) from 1955 to1963. He summarized his findings and thoseof prior studies conducted there in a compre-hensive distributional study. The localities inhis detailed species accounts included a num-ber of riparian areas throughout the country,but did not compare the species compositionof riparian areas to other habitats. Horwich &Lyon (1990) provided a list of bird speciesfound along the edges of the Belize River thatare part of the Community Baboon Sanctuary(for howler monkeys) in Belize. Miller &Miller (1998) summarized the ornithologicalwork conducted in Belize since Russell’s 1964study. In this paper we present the results of a4-year study on the bird species present in riv-

erine forest along the Sibun River in centralBelize.

METHODS

Study area. The study was conducted along thenorthern edge of Runaway Creek Nature Pre-serve. The 2432 ha (24.3 km2) Runaway CreekNature Preserve (RCNP) is a private pro-tected area owned and managed by the Foun-dation for Wildlife Conservation, Inc.Approximately 6.4 km of the Sibun Riverform the northern boundary of the RCNP.The study area encompassed approximately20 ha within the middle reaches of the SibunRiver, at 17°21’N and 088°29’W, and 38 ma.s.l. Mean annual rainfall in central Belize(Belmopan) is about 2020 mm. Mean dailytemperatures range from a low of 22.8ºC inJanuary to a high of 28.7ºC in May (BelizeNMS 2005). Mean temperature at the studysite during the study was 22.6ºC. Annualfloods inundate the study area during the Julyto December rainy season. The study area islocated in the transition zone between sub-tropical moist and subtropical wet forest lifezones (Hartshorn et al. 1984) in EcoregionNT0154 (the Petén-Veracruz moist forest,NGS & WWF 2005). The vegetation isdescribed as tropical evergreen seasonal allu-vial forest (Meerman 1999). The riverine for-est studied was not affected by fragmentation,as it was bordered to the south, east and westby tropical evergreen seasonal forest. Thestudy site was surrounded by approximately210 ha of unfragmented riverine forest; anadditional approximately 1097 ha of tropicalevergreen seasonal forest bordered the site onthe west and south. No evidence of recenthuman disturbance was present at the studysite, but some sapodilla (Manilkara sapota)trees had old slash marks indicating past useby chicleros.

Avifaunal sampling. The range of hours spent at

334

BELIZE SIBUN RIVERINE FOREST BIRDS

the site each day was 3.3–11.5 (mean + SD =7.7 + 2.3 h). Effort at the site was as follows:in 2000, 1 day in February and 2 days inMarch (27.5 h, 327.3 mist-net hours); in 2001,6 days in March (51.8 h, 571.3 mist-nethours); in 2001–2002, 16 days (4 days eachmonth) from December 2001 through March2002 (117.7 h, 1217.6 mist-net hours); and in2002–2003, 14 days (3–4 days each month)from December 2002 through March 2003(103.3 h, 1055.9 mist-net hours). From 2000through 2003, 300.4 h were spent at the site,and the total mist-net hours were 3172.1.

Because the study took place mainly dur-ing the non-breeding season and territorialsinging is infrequent during this time period(Lynch 1995), we utilized a sampling tech-nique modified from the Long Point BirdObservatory migration monitoring protocol(McCracken et al. 1993). The bird speciespresent were sampled using mist-netting, astandardized census and casual observations.

The mist nets used in this study werenylon, 12 x 2.6 m, of 30-mm mesh size with 4shelves. Nets were set beginning 20 m fromthe river in order to sample areas dominatedby spiny bamboo (Guadua longifolia) and thenspaced randomly from this net to the forestinterior. In 2000 and 2001, 12–14 nets wereset at ground level and two nets were elevated(Albanese & Piaskowski 1999) to 5–7 mabove ground level. In addition, in 2000 and2001, one 30-mm mesh net measuring 6 x 5.2m was used to sample stratum startingapproximately 21 m above ground level. In2000 and 2001, mist nets were opened justbefore sunrise and operated for 6.2–11.5 hper day, weather permitting. During the 2001–2002 and 2002–2003 field seasons, nets wereoperated for 4 consecutive days each monthin two different locations within the studyarea. On days one and two, 11 ground-levelnets and one elevated net were operated. Ondays three and four, nine ground-level netsand one elevated net were operated. Mist nets

were operated for up to 10 h the first day ofthe rotation and for up to 6 h the second dayof the rotation, weather permitting. We stan-dardized mist-netting capture results using nethours. Net hours were calculated by summingthe number of hours each 12 m net was oper-ated (one net hour = one 12 m net open forone hour). We used the number of birds cap-tured per 100 net hours to estimate the rela-tive abundance of birds captured in mist nets.Included in these calculations were new birdscaptured as well as recaptured individuals thatwere banded at the site in previous field sea-sons. All North American migrants captured,except hummingbirds, were banded using aU.S. Bird Banding Laboratory aluminum legband. All resident birds captured, excepthummingbirds, also were banded with auniquely numbered aluminum leg band.Breeding condition was determined by thepresence of a brood patch or cloacal protu-berance, as described in Burton & DeSante(1998). We considered only species with abrood patch or cloacal protuberance score of>1 as being in breeding condition.

To sample birds not captured in mist nets,we also recorded birds detected by visual andauditory observations using two methods. Acensus route traversing the study area wasestablished. This census area started at theriverbank and moved through the entire areain which nets were set. An observer began towalk this route each day just before sunriseand before mist nets were opened, recordingall bird species seen and heard. The censusroute took approximately 45 min to complete.In addition, researchers recorded birdsdetected throughout the day. Birds detectedwithin 2 h of sunrise were counted as “cen-sused” and those detected thereafter wererecorded as “observed.” At the end of the day,all observers conferred and estimates of thetotal number of each species detected duringthe census and observation periods werecompiled according to the methods of

335

336

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OW

SKI E

T AL.

TABLE 1. Species of conservation concern detected at the study site.

Spec Abundance at study site4

Belize seasonality5

NeoAnhBareSnoLittlJabirWooKinSwaOrnWhiWhiRedWooBlueProtWorSwaKen

RRURCCURRRUCCCURCRU

RRRRMRRRSRRRRMMTMMM

1The ution (BD), non-breeding distribution(ND ated as follows: (highest of TB or TNsco ghest concern). (Rich et al. 2004).

2The pulation size, threats to breeding andnon

3The ncern in Belize (Miller & Miller 1997).The

4Abu Rare, detected on < 20% of days.5Bel Belize, does not breed in Belize; T =Tra s).

ies PIF Combined score & status1

NAWCP category2 Regional and Belize conservation concern3

tropic Cormorant (Phalacrocorax brasilianus)inga (Anhinga anhinga)-throated Tiger-Heron (Tigrisoma mexicanum)

wy Egret (Egretta thula)e Blue Heron (Egretta caerulea)u (Jabiru mycteria)d Stork (Mycteria americana)

g Vulture (Sarcoramphus papa)llow-tailed Kite (Elanoides forficatus)ate Hawk-Eagle (Spizaetus ornatus)te-crowned Parrot (Pionus senilis)te-fronted Parrot (Amazona albifrons)-lored Parrot (Amazona autumnalis)d Thrush (Hylocichla mustelina)-winged Warbler (Vermivora pinus)honotary Warbler (Protonotaria citrea)m-eating Warbler (Helmitheros vermivorum)inson's Warbler (Limnothlypis swainsonii)tucky Warbler (Oporornis formosus)

16: Watch List

14: Watch List15: Watch List15: Watch List14: Watch List14: Watch List14: Watch List

ModerateModerate

HighHighHighHighHigh

XXX

XXXX

X

se Neotropical migrant Partners in Flight (PIF) scores take into account population size (PS), breeding distrib), threats to breeding (TB) and non-breeding (TN), and population trend (PT). The Combined score is calcul

res) + (highest of BD or ND scores) + PT + PS. Combined scores can range from 4 (relatively secure) to 20 (hise North American Waterbird Conservation Plan (NAWCP) categories take into account population trend, po-breeding, breeding and non-breeding distribution (Kushlan et al. 2002).se species are of regional conservation concern (in Mexico and/or Guatemala) and are also of conservation co assessment for Belize was based on each species distribution and range (Miller & Miller 1997).ndance codes: C = Common, detected on > 50% of days; U = Uncommon, detected on 20%-49% of days; R =

ize seasonality codes: R = Resident, present year-round; M = Migrant, spends non-breeding season (“winter”) innsient, present during migration; S = Seasonal resident, migrates to Belize to breed (also called breeding migrant


McCracken et al. (1993), with care taken toavoid double counting of individual birds. Wewere able to collect data for the standard 2-hcensus period each day, but the length of thecasual observation period varied considerably.

We estimated the abundance of each spe-cies at the site by calculating the percent ofdays that the species was detected by anymethod. Species were considered common ifthey were detected on > 50% of days, uncom-mon if detected on 20–49% of days and rareif detected on < 20% of days.

We used EstimateS (Colwell 2004) scaledby samples (number of sampling days) tocompute species accumulation curves for thespecies detected by census and mist-netting.EstimateS uses repeated re-sampling of allpooled samples to calculate the sample-basedrarefaction (species accumulation) curve. Tocompute the asymptote for the species accu-mulation curves, we used the Michaelis-Menton species richness estimation function(Colwell & Coddington 1994) computed byEstimateS. This method computes the esti-mated total species richness based on succes-sively larger numbers of samples from thedata set.

Assessing the conservation importance of the speciesdetected at the study site. We defined Neotropicalmigrants or transients as those species inwhich all or part of their populationsbreed north of the Tropic of Cancer andspend the non-breeding season south of theTropic of Cancer (DeGraaf & Rappole 1995).For Neotropical migrant landbirds, we usedPartners in Flight (PIF) Combined Scores(Rich et al. 2004). These scores take intoaccount population size and trends, distribu-tion, and threats during breeding and non-breeding seasons and allow for determinationof species of continental importance, suchas Watch List species. Details on how thescores are calculated are listed at the bottomof Table 1.

For waterbirds we used the conservationstatus assessment categories of Kushlan et al.(2002). Information on restricted-rangeendemics and species that are considered tobe of conservation concern in Belize wasbased on Miller & Miller (1997).

Vegetation. We conducted vegetation measure-ments at mist-net locations based on themethods of Ralph et al. (1993), Howe et al.(1997), Mallory (1997) and Martin et al.(1997). Ground-level mist nets were groupedaccording to the predominant vegetationpresent in the vicinity of the net, and one netwas selected randomly from each of fourgroups for analysis. Vegetation measurementswere done at both of the elevated net loca-tions. Because vegetation was cleared in astrip approximately 1 m wide on each side ofthe mist net, this cleared area was notincluded in vegetation sampling. Except forcanopy cover, which was measured at the cen-ter of the mist net lane, vegetation was sam-pled in an 11.3 m radius semicircle on bothsides of the net lane, starting at the edge ofthe cleared areas.

RESULTS

Avifaunal sampling. A total of 196 species wasdetected, including 151 (77.0%) residents, 38(19.4%) migrants and/or transients, 4 (2.0%)seasonal residents, and 3 (1.5%) resident/migrants (Table 2). Neotropical migrantsand/or transients of 36 species represented18.4% of the total. One-hundred sixty specieswere detected during censuses, 95 weredetected by mist-netting, 14 were detectedonly by mist-netting, and 17 were detectedonly during casual observations (Table 2).Seventy-nine species were considered com-mon at the site, 39 were uncommon and 78were rare.

The species most frequently detected bycensus were the Plain Chachalaca (Ortalis

337

PIASKOWSKI ET AL.

TABLE 2. Species abundance, Belize seasonality and endemic status of bird species detected by census,mist-netting, and casual observations.

Species1 Mean number censused per day

Number of birds per 100 net-h2

Abundance at study

site3

Belize seasonality4

Great Tinamou (Tinamus major)Little Tinamou (Crypturellus soui)Plain Chachalaca (Ortalis vetula)Least Grebe (Tachybaptus dominicus)*Neotropic Cormorant (Phalacrocorax brasilianus)*Anhinga (Anhinga anhinga)*Bare-throated Tiger-Heron (Tigrisoma mexicanum)Great Blue Heron (Ardea herodias)Great Egret (Ardea alba)Snowy Egret (Egretta thula)Little Blue Heron (Egretta caerulea)Green Heron (Butorides virescens)Jabiru (Jabiru mycteria)Wood Stork (Mycteria americana)*Black Vulture (Coragyps atratus)Turkey Vulture (Cathartes aura)King Vulture (Sarcoramphus papa)Swallow-tailed Kite (Elanoides forficatus)Plumbeous Kite (Ictinia plumbea)Black-collared Hawk (Busarellus nigricollis)*Gray Hawk [Asturina nitida (plagiata)]Common Black-Hawk (Buteogallus anthracinus)Great Black-Hawk (Buteogallus urubitinga)*Roadside Hawk (Buteo magnirostris)Short-tailed Hawk (Buteo brachyurus)Zone-tailed Hawk (Buteo albonotatus)*Ornate Hawk-Eagle (Spizaetus ornatus)*Collared Forest-Falcon (Micrastur semitorquatus)Laughing Falcon (Herpetotheres cachinnans)Aplomado Falcon (Falco femoralis)*Bat Falcon (Falco rufigularis)Spotted Wood-Quail (Odontophorus guttatus)Ruddy Crake (Laterallus ruber)Gray-necked Wood-Rail (Aramides cajanea)Sungrebe (Heliornis fulica)*Killdeer (Charadrius vociferus)*Spotted sandpiper (Actitis macularius)*Pale-vented Pigeon (Patagioenas cayennensis)Scaled Pigeon (Patagioenas speciosa)Red-billed Pigeon (Patagioenas flavirostris)Short-billed Pigeon (Patagioenas nigrirostris)

0.030.1519.510.000.000.000.130.080.130.050.460.031.620.001.030.740.030.080.030.000.030.050.000.180.150.000.001.131.000.000.080.081.440.210.000.000.004.102.030.081.74

0.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.000.00

RRCRRRUUURCRCUCCRRURRRRCURRCCRURCRRRRCCRC

RRRRRRRRRRMRRRR

R/MRSSRRRRRRMRRRRRRRRRMMRRRR

338


TABLE 2. Continued.



Abundance at study

site3

Belize seasonality4

Ruddy Ground-Dove (Columbina talpacoti)Blue Ground-Dove (Claravis pretiosa)White-tipped Dove (Leptotila verreauxi)Gray-fronted Dove [Leptotila rufaxilla (plumbeiceps)]Gray-chested Dove (Leptotila cassini)Ruddy Quail-Dove (Geotrygon montana)Olive-throated Parakeet (Aratinga nana) White-crowned Parrot (Pionus senilis)MAE

White-fronted Parrot (Amazona albifrons)MAE

Red-lored Parrot (Amazona autumnalis)Squirrel Cuckoo (Piaya cayana)Striped Cuckoo (Tapera naevia)Groove-billed Ani (Crotophaga sulcirostris)Vermiculated Screech-owl (Megascops guatemalae)Mottled Owl (Ciccaba virgata)Common Pauraque (Nyctidromus albicollis)White-collared Swift (Streptoprocne zonaris)Vaux's Swift (Chaetura vauxi)Long-billed (Long-tailed) Hermit (Phaethornis longirostris)Stripe-throated (Little) Hermit (Phaethornis striigularis)Wedge-tailed Sabrewing (Campylopterus curvipennis)MAE

White-necked Jacobin (Florisuga mellivora)†

Green-breasted Mango (Anthracothorax prevostii)White-bellied Emerald (Amazilia candida)MAE

Rufous-tailed Hummingbird (Amazilia tzacatl)Buff-bellied Hummingbird (Amazilia yucatanensis)NMAE

Ruby-throated Hummingbird (Archilochus colubris)†

Black-headed Trogon (Trogon melanocephalus)MAE

Violaceous Trogon (Trogon violaceus)Blue-crowned Motmot (Momotus momota)Ringed Kingfisher (Ceryle torquatus)Green Kingfisher (Chloroceryle americana)American Pygmy Kingfisher (Chloroceryle aenea)White-necked Puffbird (Notharchus macrorhynchos)*Rufous-tailed Jacamar (Galbula ruficauda)Collared Aracari (Pteroglossus torquatus)Keel-billed Toucan (Ramphastos sulfuratus)Black-cheeked Woodpecker (Melanerpes pucherani)Golden-fronted Woodpecker (Melanerpes aurifrons)Smoky-brown Woodpecker (Veniliornis fumigatus)Golden-olive Woodpecker (Piculus rubiginosus)Lineated Woodpecker (Dryocopus lineatus)

0.085.333.002.361.230.052.030.563.237.230.640.030.180.050.361.030.050.870.590.620.000.000.000.794.050.000.001.381.671.360.230.000.000.001.081.511.790.053.030.181.721.18

0.000.160.000.090.060.030.000.000.000.000.000.000.000.000.000.000.000.000.630.280.030.060.030.691.510.090.060.000.000.060.000.030.030.000.090.000.000.000.090.570.030.00

RCCCURCUCCCRRRUURRCCRRRCCRRCCCUURRCUCRCUCC

RRRRRRRRRRRRRRRRRRRRRRRRRRMRRRRRRRRRRRRRRR

339

PIASKOWSKI ET AL.

TABLE 2. Continued.



Abundance at study

site3

Belize seasonality4

Pale-billed Woodpecker (Campephilus guatemalensis)MAE

Rufous-breasted Spinetail (Synallaxis erythrothorax)MAE

Plain Xenops (Xenops minutus)Tawny-winged Woodcreeper (Dendrocincla anabatina)MAE

Ruddy Woodcreeper (Dendrocincla homochroa)Olivaceous Woodcreeper (Sittasomus griseicapillus)Wedge-billed Woodcreeper (Glyphorynchus spirurus)†

Northern Barred-Woodcreeper (Dendrocolaptes sanctithomae)Ivory-billed Woodcreeper (Xiphorhynchus flavigaster)MAE

Streak-headed Woodcreeper (Lepidocolaptes souleyetii)†

Great Antshrike (Taraba major)Barred Antshrike (Thamnophilus doliatus)Dusky Antbird (Cercomacra tyrannina)Black-faced Antthrush [Formicarius analis (moniliger)]Yellow-bellied Tyrannulet (Ornithion semiflavum)MAE

Northern Beardless-Tyrannulet (Camptostoma imberbe)Greenish Elaenia (Myiopagis viridicata)Yellow-bellied Elaenia (Elaenia flavogaster)Ochre-bellied Flycatcher (Mionectes oleagineus)Sepia-capped Flycatcher (Leptopogon amaurocephalus)Northern Bentbill (Oncostoma cinereigulare)Slate-headed Tody-Flycatcher (Poecilotriccus sylvia)Common Tody-Flycatcher (Todirostrum cinereum)Eye-ringed Flatbill (Rhynchocyclus brevirostris)Yellow-olive Flycatcher (Tolmomyias sulphurescens)Stub-tailed Spadebill (Platyrinchus cancrominus)MAE

Royal Flycatcher (Onychorhynchus coronatus)Tropical Pewee (Contopus cinereus)Yellow-bellied Flycatcher (Empidonax flaviventris)†

White-throated Flycatcher (Empidonax albigularis)†,MAE

Least Flycatcher (Empidonax minimus)†

Bright-rumped Attila (Attila spadiceus)Dusky-capped Flycatcher (Myiarchus tuberculifer)Brown-crested Flycatcher (Myiarchus tyrannulus)Great Kiskadee (Pitangus sulphuratus)Boat-billed Flycatcher (Megarynchus pitangua)Social Flycatcher (Myiozetetes similis)Tropical Kingbird (Tyrannus melancholicus)Couch's Kingbird (Tyrannus couchii)Thrush-like Schiffornis (Schiffornis turdina)Rose-throated Becard (Pachyramphus aglaiae)Masked Tityra (Tityra semifasciata)

1.5911.590.100.790.770.280.001.542.790.004.6210.679.260.720.210.051.100.330.030.033.100.641.230.051.280.230.030.380.000.000.003.361.640.791.820.491.130.720.080.050.100.23

0.001.320.000.790.850.000.060.090.660.130.350.850.950.090.000.000.320.030.760.030.600.280.000.000.570.000.060.000.030.030.160.540.320.000.000.000.000.000.000.030.060.00

CCRCCURCCRCCCUURCUURCCCRCURURRRCCUCCCURRRU

RRRRRRRRRRRRRRRRRRRRRRRRRRRRMMMRRSRRRRRRRR

340


TABLE 2. Continued.



Abundance at study

site3

Belize seasonality4

White-collared Manakin (Manacus candei)MAE

Red-capped Manakin (Pipra mentalis)White-eyed Vireo (Vireo griseus)Mangrove Vireo [Vireo pallens (semiflavus)]MAE

Yellow-throated Vireo (Vireo flavifrons)Yellow-green Vireo (Vireo flavoviridis)Lesser Greenlet (Hylophilus decurtatus)Rufous-browed Peppershrike (Cyclarhis gujanensis)Brown Jay (Cyanocorax morio)MAE

Tree Swallow (Tachycineta bicolor)Northern Rough-winged Swallow (Stelgidopteryx serripennis)*Spot-breasted Wren (Thryothorus maculipectus)MAE

White-bellied Wren (Uropsila leucogastra)NMAE

White-breasted Wood-Wren (Henicorhina leucosticta)Long-billed Gnatwren (Ramphocaenus melanurus)Blue-gray Gnatcatcher (Polioptila caerulea)*Wood Thrush (Hylocichla mustelina)Clay-colored Robin (Turdus grayi)Gray Catbird (Dumetella carolinensis)Blue-winged Warbler (Vermivora pinus)Tennessee Warbler (Vermivora peregrina)Orange-crowned Warbler (Vermivora celata)†

Yellow Warbler (Dendroica petechia) Chestnut-sided Warbler (Dendroica pensylvanica)*Magnolia Warbler (Dendroica magnolia)Black-throated Green Warbler (Dendroica virens)Yellow-throated Warbler (Dendroica dominica)Black-and-white Warbler (Mniotilta varia)American Redstart (Setophaga ruticilla)Prothonotary Warbler (Protonotaria citrea)Worm-eating Warbler (Helmitheros vermivorum)Swainson's Warbler (Limnothlypis swainsonii)†

Ovenbird (Seiurus aurocapilla)Northern Waterthrush (Seiurus noveboracensis)Louisiana Waterthrush (Seiurus motacilla)†

Kentucky Warbler (Oporornis formosus)Common Yellowthroat (Geothlypis trichas)Hooded Warbler (Wilsonia citrina)Yellow-breasted Chat (Icteria virens)Gray-throated Chat (Granatellus sallaei)†, YPE

Gray-headed Tanager (Eucometis penicillata)Red-throated Ant-Tanager (Habia fuscicauda)

1.180.180.440.380.050.052.380.2614.318.590.0013.790.080.050.870.005.673.6911.150.100.030.000.030.004.490.280.050.102.690.030.030.000.131.620.000.151.080.490.920.000.368.72

1.201.010.000.000.000.000.060.000.000.000.002.300.000.000.190.002.300.445.300.280.160.030.030.001.290.030.000.350.410.000.820.091.260.280.030.630.691.230.500.031.361.13

CUUURRCUCRRCRRCRCCCURRRRCURUCRCRCCRUCCCRCC

RRMRMSRRRM

R/MRRRR

R/MMRMM

M/TMMMMMMMMTMMMM

M/TMMMMRRR

341

PIASKOWSKI ET AL.

TABLE 2. Continued.



Abundance at study

site3

Belize seasonality4

Summer Tanager (Piranga rubra)Scarlet Tanager (Piranga olivacea)Crimson-collared Tanager (Ramphocelus sanguinolentus)MAE

Passerini's Tanager (Ramphocelus passerinii)MAE

Blue-gray Tanager (Thraupis episcopus)Yellow-winged Tanager (Thraupis abbas)MAE

Red-legged Honeycreeper (Cyanerpes cyaneus)Variable Seedeater (Sporophila americana)†

White-collared Seedeater (Sporophilia torqueola)Thick-billed Seed-Finch (Oryzoborus funereus)Blue Seedeater (Amaurospiza concolor)†

Green-backed Sparrow (Arremonops chloronotus)NMAE

Grayish Saltator (Saltator coerulescens)Buff-throated Saltator (Saltator maximus)Black-headed Saltator (Saltator atriceps)MAE

Black-faced Grosbeak (Caryothraustes poliogaster)MAE

Blue-black Grosbeak (Cyanocompsa cyanoides)Indigo Bunting (Passerina cyanea)†

Melodious Blackbird (Dives dives)MAE

Giant Cowbird (Molothrus oryzivorus)Black-cowled Oriole (Icterus prosthemelas)MAE

Orchard Oriole (Icterus spurius)Yellow-backed Oriole (Icterus chrysater)*,NMAE

Yellow-tailed Oriole (Icterus mesomelas)Baltimore Oriole (Icterus galbula)Yellow-billed Cacique (Amblycercus holosericeus)Montezuma Oropendola (Psarocolius montezuma)MAE

Scrub Euphonia (Euphonia affinis)MAE

Yellow-throated Euphonia (Euphonia hirundinacea)MAE

0.440.030.310.310.410.151.820.000.130.280.002.156.725.087.640.054.440.000.820.081.050.690.0013.690.2311.443.540.131.69

0.030.000.190.190.000.060.350.130.090.130.280.630.350.410.160.000.440.090.000.000.060.130.000.060.060.730.000.000.16

CRUUURURRRRCCCCRCRRRCURCUCCRC

MTRRRRRRRRRRRRRRRMRRRMRRMRRRR

1Order follows AOU (2005).2Includes newly banded birds and recaptures from prior field seasons. 3Abundance codes: C = Common, detected on > 50% of days; U = Uncommon, detected on 20%–49%of days; R = Rare, detected on < 20% of days.

4Belize seasonality codes: R = Resident, present year-round; M = Migrant, spends non-breeding season(“winter”) in Belize, does not breed in Belize; T = Transient, present during migration; S = Seasonal res-ident, migrates to Belize to breed (also called breeding migrants).

*Detected only during the casual observation period.†Detected only through mist-netting.MAEMiddle America endemics (Miller & Miller 1997). NMAENorthern Middle America endemics (Miller & Miller 1997). YPEYucatan Peninsula endemics (Miller & Miller 1997).

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vetula), Brown Jay (Cyanocorax morio), Spot-breasted Wren (Thryothorus maculipectus),Yellow-tailed Oriole (Icterus mesomelas) andRufous-breasted Spinetail (Synallaxis erythrotho-rax) (Table 2).

A total of 1167 birds of 95 species werecaptured in mist nets during the study, and389 individuals were recaptured. Of the recap-tures, 190 (48.8%) were banded at the site inprevious field seasons. The species detectedmost frequently by mist-netting were the GrayCatbird (Dumetella carolinensis), Spot-breastedWren, Wood Thrush (Hylocichla mustelina),Rufous-tailed Hummingbird (Amazilia tzacatl),Gray-headed Tanager (Eucometis penicillata),and Rufous-breasted Spinetail. Fourteen spe-cies were detected only by mist-netting (Table2). Five species, the Wedge-tailed Sabrewing(Campylopterus curvipennis), Green-breastedMango (Anthracothorax prevostii), Buff-belliedHummingbird (Amazilia yucatanensis), GreenKingfisher (Chloroceryle americana) and Ameri-can Pygmy-Kingfisher (Chloroceryle aenea) weredetected by both mist-netting and casualobservations but not during the censusperiod.

Continuing observations beyond the endof the census period (2 h after sunrise)allowed for the detection of additional spe-cies. Seventeen species were detected onlyduring the observation period (Table 2). TheWood Stork (Mycteria americana), Black-collared Hawk (Busarellus nigricollis), Zone-tailed Hawk (Buteo albonotatus), AplomadoFalcon (Falco femoralis) and Northern Rough-winged Swallow (Stelgidopteryx serripennis) weredetected soaring over the study area only laterin the day.

Operation of two elevated nets provedworthwhile as the Yellow-bellied Elaenia(Elaenia flavogaster), Orange-crowned Warbler(Vermivora celata), Black-throated Green War-bler (Dendroica virens), White-collared Seed-eater (Sporophila torqueola), and Yellow-tailedOriole were captured only in elevated nets.

The Golden-olive Woodpecker (Piculus rubigi-nosus), Yellow Warbler (Dendroica petechia),Black-cowled Oriole (Icterus prosthemelas),Orchard Oriole (Icterus spurius), and BaltimoreOriole (Icterus galbula) were captured only inthe canopy net. The Tennessee Warbler (Ver-mivora peregrina), Yellow-winged Tanager(Thraupis abbas), and Red-legged Honey-creeper (Cyanerpes cyaneus) were captured inboth the elevated and canopy nets but not innets operated at ground level.

We observed few reproductive behaviors(carrying nesting material or food, courtshipbehaviors) during the study period. BrownJays were observed carrying nesting materialin February 2002 and March 2003. A Bare-throated Tiger-Heron (Tigrisoma mexicanum)and a Jabiru (Jabiru mycteria) nested at the site(see Species accounts).

Table 3 shows for each species the earliestdate of evident reproductive activity at thetime of banding or recapture. Twenty-threeindividuals of 11 species had a brood patchscore of 2–5, indicating that they were breed-ing in the area (Brewer et al. 1991). All werecaptured during March and all were Belizeresident species. Five individuals of three spe-cies had a cloacal protuberance, indicatingthat these male birds were approaching readi-ness to breed or in breeding condition (Pyle1997). All birds with cloacal protuberanceswere captured in March (Table 3).

The species accumulation curves for sam-pling by census and mist-netting are shown inFigs 1a and 1b. The curve for sampling bycensus (Fig 1a) approached an asymptote; thecalculated asymptote was 159, indicating thatsampling by census was complete. The speciesaccumulation curve for mist-netting (Fig 1b)did not approach an asymptote. The calcu-lated asymptote was 105, indicating that sam-pling by this method was not complete.

Assessing the conservation importance of the speciesdetected at the study site. Thirty-one species

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detected at the site are found only in MiddleAmerica (Table 2, Miller & Miller 1997). Fiveof these have more restricted ranges; theBuff-bellied Hummingbird, White-belliedWren (Uropsila leucogastra), Green-backedSparrow (Arremonops chloronotus), and Yellow-backed Oriole (Icterus chrysater) are northernMiddle America endemics; the Gray-throatedChat (Granatellus sallaei) is a Yucatan Peninsulaendemic.

Table 1 lists the 19 species that are of con-servation concern based on Miller & Miller(1997), Kushlan et al. (2002), and Rich et al.(2004). Of the 38 species of migrants and/ortransients detected during this study, seven(18.4%) are listed as being PIF Watch Listspecies. Of the 14 species of waterbirdsdetected at the site, five (35.7%) are catego-rized as being at high risk and two at moder-ate risk (14.3%) by Kushlan et al. (2002). Eightspecies (4.1% of the total) are listed as beingof conservation concern in both Belize andthe region by Miller & Miller (1997). None ofthe species detected at the site are on the

IUCN red list of threatened species (IUCN2004).

Vegetation. The riparian forest studied con-sisted of an area dominated by spiny bamboonear the river edge that transitioned into for-ested areas dominated by cohune (Ateleacohune) and coccoloba (Coccoloba schiedeana),with scattered large, emergent quamwood(Schizolobium parahybum) trees. A few large fig(Ficus sp.) trees were also present along theriverbank bordering the study area, and twolarge fig trees (approximately 80 cm dbh)were present within the study area. A smallforest gap of approximately 20 m2 waspresent near the center of the study area. Adense cover of wild cane (Tripsacum andersonii)bordered the eastern edge of the study area.

No differences were evident in the vegeta-tion sampled at the ground and elevated nets(data not shown); so the data were combinedfor the following summaries. The mean can-opy cover was 88%. Maximum tree heightwas 45 m. The numbers of sublayers evident

TABLE 3: Birds captured at the study site that were in reproductive condition1.

Species CP grade2 BP grade2 Earliest date in reproductive condition

Smoky-brown Woodpecker (Veniliornis fumigatus)Golden-olive Woodpecker (Piculus rubiginosus)Great Antshrike (Taraba major)Barred Antshrike (Thamnophilus doliatus) Dusky Antbird (Cercomacra tyrannina)Black-faced Antthrush [Formicarius analis (moniliger)]Yellow-olive Flycatcher (Tolmomyias sulphurescens)Spot-breasted Wren (Thryothorus maculipectus)Yellow-winged Tanager (Thraupis abbas)Red-legged Honeycreeper (Cyanerpes cyaneus)Red-legged Honeycreeper (Cyanerpes cyaneus)Blue-black Grosbeak (Cyanocompsa cyanoides)Yellow-billed Cacique (Amblycercus holosericeus)Yellow-throated Euphonia (Euphonia hirundinacea)

00000000202002

23222323050350

3 March 20016 March 20016 March 20013 March 200122 March 20014 March 20013 March 20013 March 200122 March 20013 March 20013 March 20013 March 200121 March 20004 March 2001

1All of these species are resident birds, present in Belize year-round.2Birds with a cloacal protuberance (CP) or brood patch (BP) grade > 1 are included in this list.

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for each vegetation category were as follows:trees 1–3, shrubs 2–5, and herbs 2–3. Herbcover varied from few, with small cover, to75%. The most common herbs were ferns,Dieffenbachia sp., Heliconia sp., vines and lianas.

In areas where the vegetation was dominatedby spiny bamboo, a dense concentration ofthorny vines and lianas such as haul-me-back(Mimosa sp.) and tear coat (Byttneria aculeata)were also present. Graminoid (grass, sedge

FIG. 1. Species accumulation curves for birds sampled by census and mist-netting. (a) Sampling by cen-sus, (b) Sampling by mist-netting.

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PIASKOWSKI ET AL.

and rush) cover varied from solitary, withsmall cover, to 50% cover. Leaf litter withcover of > 75% was present in all areas sam-pled. Moss cover ranged from little to < 25%.

Species accounts. Information documenting the observationsof the less common species, those nesting atthe site, and those whose migration status ispoorly understood appear below.

Bare-throated Tiger-Heron (Tigrisoma mexi-canum). This species was observed on eightdifferent dates from December throughMarch and was categorized as rare at the site.One was observed nest building in the sametree as the Jabiru on 22 March 2002. Jones(2003) described this species as a locally fairlycommon resident on the Belize mainland.

Jabiru (Jabiru mycteria). The Jabiru had a nestin an emergent Ceiba pentandra tree in thestudy area each year from 2001 through 2003and again in 2004 and 2005 after the studydescribed here was completed. Jabirus wereobserved near the nest in December of eachyear when our field seasons began during thismonth. Birds were observed incubating inJanuary and February and two to three nest-lings were present beginning in February.Based on our monitoring of this nest throughthe end of each breeding season (May toJune), it is believed that the nest fledged atleast two young each year, suggesting theimportance of this site to the reproductivesuccess of this species in the region. AlthoughBarnhill et al. (2005) state that Jabiru popula-tions in Belize may be increasing since gainingprotective status in 1973, the Jabiru is listed asa species of regional and Belize conservationconcern (Miller & Miller 1997) and under“Species of concern” as a Watch List speciesin Belize (Jones & Vallely 2001).

Zone-tailed Hawk (Buteo albonotatus). We

detected this species by casual observationson two consecutive days in January 2002.Jones (2003) describes this species as a veryuncommon winter visitor from mid-Octoberto mid-April. Howell & Webb (1995) describeit as a winter visitor in the Yucatan Peninsulawith the status in much of the region needingclarification.

White-throated Flycatcher (Empidonax albigu-laris). We captured and banded one individualin February 2003. It was an adult not inbreeding condition. Jones (2003) describedthis species as poorly known in Belize, a resi-dent and local winter visitor at least in thenorth, with the timing of arrival in and depar-ture from wintering areas not known.

Brown-crested Flycatcher (Myiarchus tyrannulus).We detected this species at the site each yearby census and casual observations only duringMarch. Jones (2003) describes the species as acommon summer resident in Belize fromearly March to late August, with a few over-wintering. However, Jones (2004) states thatthe Brown-crested Flycatcher is now knownto be a seasonal resident only, rather than ayear-round resident in Belize.

Blue Seedeater (Amaurospiza concolor). TheBlue Seedeater, previously unrecorded in thisarea of Belize (Howell & Webb 1995), wasdetected in the study area by mist-netting inboth 2000 and 2001 (Figueroa et al. 2004) andin 2002 and 2003. Eight individuals (fourmales and four females) were banded and tworecaptured. A female banded on 21 January2002 was recaptured on 9 December 2002,and a male captured on 5 December 2002 wasrecaptured on 22 March 2003. None of theindividuals captured was in breeding condi-tion. The Blue Seedeater is found in riversidebamboo thickets and its occurrence has alsobeen documented in another area of theSibun River (Jones 2003).

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DISCUSSION

Since mist-netting or audio-visual methodsalone can underestimate or miss some species(Rappole et al. 1998), we combined the tech-niques of censusing, casual observations andmist-netting (McCracken et al. 1993) toenhance our ability to detect the bird speciespresent at the study site. This combinationwas effective in augmenting species detectionduring this study.

Because mist nets operated at groundlevel sample avifauna that moves within 2–3m above the ground (Remsen & Good 1996),we devised an elevated net system that sam-pled areas within 5–7 m of the ground(Albanese & Piaskowski 1999) and operatedthese nets throughout the study. In 2000 and2001, we also operated one net in the canopywhere the top of the net was at a height ofapproximately 21 m. Due to staffing changesafter 2001, we were not able to operate thecanopy net in the 2001–2002 and 2002–2003field seasons. As described above, 13 specieswere captured only in the elevated or canopynets.

Overestimation of species abundance mayhave occurred due to several factors. Hum-mingbirds and manakins are opportunisticfeeders at ephemeral resources (Terborgh etal. 1990) and therefore may have been overes-timated. Overestimation was more likely inthe case of hummingbirds because we did notmark the individuals captured. Species such asparrots and toucans that occur in flocks arealso more likely to be overestimated (Ter-borgh et al. 1990), as well as Plain Chachalacas,which were observed mainly in vocal groupsthat moved through the study area. Some ofthe species that were common at the site suchas the Rufous-breasted Spinetail, Spot-breasted Wren, Gray Catbird, and Yellow-tailed Oriole vocalized considerably and weretherefore easier to detect than other species.Underestimation of abundance may have

occurred for some of the more secretive spe-cies, especially those that were detected onlyby mist-netting.

Seventy-eight species (39.8% of the total)were estimated to be rare at the site as theywere detected on fewer than 20% of samplingdays. Rare species may have been wanderersfrom other habitats, difficult-to-observe can-opy species, large species with large homeranges, or naturally rare due to food or feed-ing behavior (Karr 1977). In addition, somemay be difficult to detect because they vocal-ize little during the non-breeding season (win-ter), such as some of the Neotropicalmigrants.

In a study of habitat associations of Neo-tropical migrants in Belize during the non-breeding season (Piaskowski et al. 2005), theWood Thrush, Gray Catbird, Worm-eatingWarbler (Helmitheros vermivorum) and HoodedWarbler (Wilsonia citrina) had a statistically sig-nificant higher proportion of individuals cap-tured in the Sibun riverine forest than in theother five habitats studied. Robbins et al.(1992) found that Gray Catbirds had a strongpreference for gallery forest (forests occurringalong rivers) in the tropics. They also foundthat the relative abundance of the WoodThrush, Kentucky Warbler (Oporornis formo-sus), and Hooded Warbler was highest in rainforests, but that many individuals were alsofound in gallery forests. Based on these stud-ies, it appears that riverine forest providesimportant non-breeding habitat for some spe-cies of Neotropical migrants.

A number of other studies of Neotropicalmigrants have been conducted in Belize andother parts of Central America during thenon-breeding season (Kricher & Davis 1986,1992; Mills & Rogers 1992, Petit et al. 1992,and Rappole et al. 1994). None studied birdsin riparian forests and therefore their resultscannot be compared to those of this study.Lynch (1989) studied the distribution of Neo-tropical migrants in the Yucatan Peninsula in

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tall floodplain forest and other habitats; how-ever, he stated that tall floodplain forest wasnot censused frequently enough to permitdetailed statistical analysis.

The species richness in this study (196) ishigher than that in two studies of birds inriparian study sites conducted in Belize south-ern hardwood forests (Brokaw & Lloyd-Evans 1987, Mallory 1991). Brokaw & Lloyd-Evans (1987) detected 178 species in threeriparian sites in the Bladen Branch Wildernessduring March; Mallory (1991) detected 146species in the Upper Raspaculo area duringJanuary and February. The higher speciesrichness in the Sibun riverine forest may bedue to more sampling effort or to a truehigher diversity of species utilizing the site.The composition of migrants in the threestudies was similar: 18.4% in the Sibun, 15.9–18.8% in the three Bladen Branch riparianareas, and 16.4% in the Raspaculo. To quan-tify the community similarity among the threesites, we used the Jaccard coefficient of com-munity (Mueller-Dombois & Ellenberg 1974).The community similarity of the Sibun river-ine forest and Bladen Branch riparian siteswas 0.490 (123 species in common, 251 totalspecies between the two); for the Sibun andRaspaculo, it was 0.437 (104 species in com-mon, 238 species between the two). In con-trast, the community similarity of theRaspaculo and Bladen Branch was 0.685 (148species in common, 216 species between thetwo) (Mallory 1991). The lower communitysimilarity among the Sibun, the BladenBranch and the Raspaculo is likely due to thedifferences in the ecological life zones sam-pled and the resultant differences in rainfalland vegetation. The Sibun riverine forest islocated in the transition zone between sub-tropical moist and subtropical wet forest lifezones (Hartshorn et al. 1984), the BladenBranch in subtropical wet forest and subtrop-ical lower montane wet forest and the Raspac-ulo in subtropical moist forest.

England (2000) assessed the resident andmigrant bird species present at Lamanai, Bel-ize, and listed the species detected in a marshcategory that included waterbirds and birdsseen in the vegetation adjacent to water.However, the site had a large lagoon, which isa very different habitat than riparian forest, soour results are not comparable. Vallely &Whitman (1997) studied the bird speciespresent at Hill Bank in northern Belize. Theirbroadleaf forest category contained what theydescribed as two swamp broadleaf foresttypes: riparian and “bajo,” but the bird speciesencountered in these were not listed sepa-rately from those of the upland broadleaf for-est, and so were not comparable to theriverine forest of our study.

The Sibun study area and surroundingforests provided expanses of habitat that wereutilized by resident and migratory species ofconservation concern (Table 1) and regionalendemics (Table 2). Seven species of Neotro-pical migrants detected at the site are listed asWatch List species by PIF (Rich et al. 2004).Watch List species have range-wide concernsand are in need of conservation attentionthroughout their range (Rich et al. 2004). Fivewaterbirds categorized as at high risk and twoof moderate risk (Kushlan et al. 2002) weredetected at the site. Other species detected atthe site that do not appear in the two abovelists include five that are of conservation con-cern in both the region and Belize (Miller &Miller 1997). Thirty-one species detected atthe site are endemic to Middle America butonly five have more restricted ranges (Table2). Stotz (1996) states that “saving endemicsmeans saving many species.” This could alsopertain to other species of conservation con-cern. Preserving riverine forests along theSibun River would protect not only these spe-cies of conservation concern and restrictedrange endemics but also the other bird speciesfound there.

Belize has nine resident parrot species

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(Jones & Vallely 2001), many of which arecaptured for use in the local pet trade. Fourparrot species were recorded during the study,three of which are listed as being of regionaland Belize conservation concern (Table 1).The study area is difficult to access due to adense border of spiny bamboo along the river,and this may provide these parrots with somelevel of protection from poaching.

Unlike the rivers in less developed andmore remote areas of Belize, the forests of theSibun River are undergoing environmentalpressures from citrus farms, residential areas,in-stream gravel mining, and logging (Boles1999). Another threat is the invasion of non-native bamboo (Bambusa vulgaris) in someareas of riparian forest along the Sibun River.Eleven villages with populations of 25–1000occur throughout the watershed. Althoughthese villages do have an impact on the river,many are also involved in its protectionthrough the Sibun Watershed Association(Boles 1999).

This study provides baseline data on thebird species present in a section of riverineforest on the Sibun River that has not beensubjected to recent human disturbance. It alsocontributes to the information available onthe avian species utilizing riparian habitats incentral Belize. The 196 bird species detectedin the 20 ha study area of riverine forest repre-sent 34.1% of the 574 bird species present inBelize (Jones 2003), indicating the diversity ofspecies that utilize this riparian habitat.Included in this species assemblage are 19species of conservation concern and 5restricted-range endemic species. Efforts topreserve the riparian habitat of the SibunRiver will protect habitat for these species aswell as for the many other bird species foundthere.

ACKNOWLEDGMENTS

We are grateful to the Zoological Society of

Milwaukee and the Foundation for WildlifeConservation, Inc. (FWC), for funding theBirds Without Borders – Aves Sin Fronteras®

(BWB-ASF) project. We thank the U.S. Fishand Wildlife Service for funding through theNeotropical Migratory Bird Conservation Actthat supported the data analysis and prepara-tion of this paper. We thank Dr. Gil Boese,founder of the BWB-ASF project and presi-dent of the FWC, for his vision and support.We thank the many BWB-ASF staff membersfor their dedication and hard work. We thankElisa Bonaccorso and David Tzul for theSpanish translation of the abstract. We thankAnna Rahn for assistance with data entry. Wethank Sharon Matola, Director of the BelizeZoo and Tropical Education Center (TEC)and Tony Garel, former manager of the TEC,for their support throughout this study. Wethank Matt Miller, the staff of Monkey Bay,and Tony Garel for their logistical supportwith canoes. We are grateful to Oliver Komarand Paula Brookmire for their valuable com-ments on this manuscript. We thank JamesReinartz for statistical assistance. This is con-tribution No. 8 of the Birds Without Borders– Aves Sin Fronteras® project.

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