Group Size and Foraging BehaviorBrandi Norris, Brittani Sanford, and Charnele Johnson

What’s the Question?

Question: Is there any patterns of group size and foraging attempts made by vultures and crows. Also, is the amount of time the birds spent foraging and walking different for birds that were alone or in a group.

Prediction: We predict that the larger the group of birds in an area the less scans and more foraging attempts will be made.

Hypothesis: If group size increases, then the need to scan more often will decrease.

Background

Social Roosting

Seasonal Roosting

Locating Food

Predation

Vulture dominance order

Crows tolerant of other crowshttp://www.radford.edu/~rsheehy/vulture/graphics/Photos/SUNP0318.JPG

What’s Being Tested?

Species: Black vulture (Coragyps atratus) and American Crow (Corvus brachyrhynchos)

Sampling: SELU vultures and crows

Results (Type of analysis): T-test

Materials

SELU Conservatory

Carcass cam

http://

www.radford.edu/~rsheehy/vulture/graphics/Photos/SUNP0282.JPG

Procedures

Recording Walking Around, Scans, and Foraging Attempts

Observations took place in mornings and nights (Sunday to Sunday)

Alone or in groups

Group Size

Timer reset if bird came or left

New bird chosen after every observation

Visit http://www.radford.edu/~rsheehy/vulture/

Results

Behavior Alone or Group? Mean ± SE T values Degrees of freedom

P value

Walking

Alone 4.20 ± 0.69 -1.67 33.3 0.1040

Group 2.93 ± 0.32

Foraging

Alone 3.15 ± 0.44 0.131 37.0 0.8964

Group 3.21 ± 0.25

Table 1. Table shows the significance in foraging and walking when a bird was alone as opposed to being in a group.

ResultsRelationship between whether a bird is alone or in a group setting with the number of scans per minute

Num

ber

of

scan

s p

er

min

ute

0

1

2

3

4

5

6

7

8

a g

Whether bird is alone (a) or in a group (g)

Mean(scans/min)

Figure 1. Graph shows the relationship between scans per minute versus whether or not the birds were alone or in groups.

Discussion

Table 1 described the relationship between walking and foraging for birds in groups minus birds that were walking around the carcass alone.

Not significant

Figure 1 measured the scans per minute between birds that were is groups versus birds that were alone.

Significant

What could be done better

longer duration of time

more accurate technology

more specific times throughout the day in which observers can watch for the birds.

Any Questions?

http://www.radford.edu/~rsheehy/vulture/graphics/Photos/SUNP0016.JPG

Sources

Buckley NJ. 1996. Food finding and the influence of information local enhancement, and communal roosting on foraging success of North American vultures. The Auk. 133(2): 473-488

Kirk DA, Houston DC. 1995. Social dominance in migrant and resident turkey vultures at carcasses: evidence for a despotic distribution? Behavioral Ecology and Sociobiology. 36(5): 323-332

Knopf FL, Knopf BA. 1983. Flocking Pattern of Foraging American Crows in Oklahoma. The Wilson Bulletin. 95: 153-155

Sweeney TM, Fraser JD. 1986 Vulture roost dynamics and Monitoring Techniques in Southwest Virginia. Wildlife Society Bulletin. 14: 49-54

Miller R, Schiestl M, Whiten A, Schwab C, Bugnyar T. 2014. Tolerance and social facilitation in the foraging behavior of free-ranging crows (Corvus corone corone; C. c. cornix). Ethology. 120(12): 1248-1255