期刊
AUK
卷 135, 期 4, 页码 857-867出版社
AMER ORNITHOLOGISTS UNION
DOI: 10.1642/AUK-18-36.1
关键词
behavioral interactions; citizen science; interspecific aggression; interspecific competition; mobbing; sociality
类别
资金
- National Science Foundation [1523695]
- Banting Canada [379958]
- Biodiversity Research Centre at the University of British Columbia
- Cornell Lab of Ornithology
- Div Of Biological Infrastructure
- Direct For Biological Sciences [1523695] Funding Source: National Science Foundation
Interspecific aggression is common in birds-Individuals regularly chase and attack members of other species. We analyzed cases of interspecific aggression between crows (American Crow [Corvus brachyrhynchos] and Northwestern Crow [C. caurinus]) and ravens (Common Raven [C. corax]) using similar to 2,000 citizen scientist observations of interspecific aggression between crows and ravens from across North America. Crows and ravens may attack one another for nonadaptive reasons, because they compete with each other for food and space, or because they are nest predators of each other. We report 3 main results. First, although ravens are much larger than crows, crows chased and attacked ravens in similar to 97% of observations. We observed this strong asymmetry in the direction of interspecific aggression throughout North America. Second, crow aggression toward ravens was most frequent during the crows' nesting season (similar to March-May), but also occurred in other seasons. Third, crows typically attacked ravens in small groups, with relatively few observations of aggression in one-on-one contests. The pattern of seasonality in crow attacks on ravens suggests that nest predation by ravens is an important factor driving interspecific aggression from crows. Aggression also occurred outside the breeding season, particularly in the winter, indicating either that crows compete with ravens for resources at this time of year or that crows preemptively harass potential nest predators in advance of the breeding season. This study is an example of how citizen scientists can contribute to the study of behavioral interactions of birds at a continental scale.
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