Injury and paternity loss in cooperatively breeding American Crows


  • Andrea K. Townsend,

    Corresponding author
    1. Fuller Evolutionary Biology Program, Cornell Lab of Ornithology, 159 Sapsucker Woods Road, Ithaca, New York 14850, USA
    Search for more papers by this author
    • Current address: Department of Wildlife, Fish, & Conservation Biology, University of California at Davis, One Shields Ave, Davis, CA 95616

  • Anne B. Clark,

    1. Department of Biological Sciences, Binghamton University, New York 13902, USA
    Search for more papers by this author
  • Kevin J. McGowan

    1. Education Program, Cornell Lab of Ornithology, 159 Sapsucker Woods Road, Ithaca, New York 14850, USA
    Search for more papers by this author



ABSTRACT Although survivable injuries have been documented in several species of birds, little is known about the social and reproductive consequences of such injuries. We examined relationships between injuries and group composition, reproductive output, and paternity of male breeders in 27 family groups of American Crows (Corvus brachyrhynchos) using 96 broods sampled from 2004 to 2009. Injuries and permanent disfigurement of wings or feet were sustained by 25.9% (7/27) of dominant male breeders. Injured male breeders had smaller broods (2.13 vs. 3.38 nestlings per brood for injured vs. uninjured breeders), lost more paternity (48% vs. 13% extrapair young per brood), and had more adult male auxiliaries in their groups (1.63 vs. 0.65 auxiliaries per group) than uninjured birds. Some of the variation in reproductive partitioning, extrapair paternity rates, and group composition among American Crow family groups can therefore be explained by injuries to male breeders. These results suggest that injuries could account for some of the unexplained variation in the rates and distribution of extrapair paternity across populations and taxa, as well as some of the variation in reproductive skew among cooperatively breeding birds.


Aunque el sobrevivir con lesiones ha sido documentado en varias especies de aves, se sabe muy poco sobre las consecuencias reproductivas y sociales de tales heridas. Examinamos la relación entre heridas y la composición de grupos, progenie producida y la paternidad de machos en 27 grupos familiares de Corvus brachyrhynchos, utilizando una muestra de 96 camadas estudiadas entre el 2004 y el 2009. El 25.9% (7/27) de los machos reproductivos dominantes, presentaron heridas y lesiones permanente de alas y patas. Los machos reproductivos con heridas tuvieron camadas más pequeñas (2.13 vs. 3.38 pichones por camadas de machos con heridas vs. reproductivos sanos), perdieron mayor paternidad (48% vs. 13% pichones con otras parejas por camada), y tuvieron mayor número de machos adultos auxiliares en sus grupos (1.63 vs. 0.65 auxiliares por grupo) que aves sin lesiones. Algunas de las variaciones en la repartición reproductiva, tasas de paternidad con otros individuos que no son su pareja, y la composición de grupos entre familias de cuervos pueden entonces ser explicados por la presencia de lesiones en los machos dominantes reproductivos. Estos resultados sugieren que las lesiones pueden ser responsables de variaciones inexplicables, en las tasas y distribución de paternidad extraparejas entre poblaciones y las taxas, al igual que de algunas variaciones en la reproducción cooperativa de aves.