Department of Bioscience, Aarhus University, Rønde, Denmark.
Ecologie Systématique Evolution, Université Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, Orsay Cedex, France.
PLoS One. 2021 Mar 30;16(3):e0248615. doi: 10.1371/journal.pone.0248615. eCollection 2021.
Prey size selection in some bird species is determined by the size of the beak. However, we assumed for bird species swallowing whole prey that a cognitive process may be involved. As cognitive feature, brain mass was used. We hypothesized that the mass of the brain was more strongly positively correlated with prey size than morphological features such as beak volume, gizzard mass and body mass. We tested this hypothesis on eiders Somateria mollissima that swallow the prey whole, by using mean and maximum size of nine prey categories. Eiders were collected at the main wintering grounds in Denmark. As index of brain mass we used head volume, which is positively correlated with brain mass (r2 = 0.73). Head volume of eiders was significantly, positive correlated with mean and maximum size of blue mussels Mytilus edulis, razor clams Ensis directus and all prey sizes combined and the maximum size of draft whelk Hinia reticulata and conch Buccinum undatum. Gizzard mass was also significantly positively correlated with maximum size of draft whelk and conch. Beak volume and body mass was not significantly correlated with the size of any of the nine food items. Analyses of effect size for organs showed that head volume was positively related to prey size, whereas beak volume, gizzard mass and body mass did not show a significant positive relationship. These results indicate that cognitive processes connected to brain mass may be involved in prey size selection by eiders.
在某些鸟类物种中，捕食者的体型选择取决于喙的大小。然而，我们假设对于那些整体吞食猎物的鸟类物种，可能涉及到认知过程。作为认知特征，我们使用了脑质量。我们假设脑质量与猎物大小的相关性比喙体积、砂囊质量和体重等形态特征更强。我们通过使用 9 种猎物类别的平均和最大尺寸，对整体吞食猎物的绒鸭 Somateria mollissima 进行了检验。绒鸭是在丹麦的主要越冬地收集的。我们使用与脑质量正相关的头体积（r2 = 0.73）作为脑质量的指标。绒鸭的头体积与贻贝 Mytilus edulis、长牡蛎 Ensis directus 以及所有猎物的平均和最大尺寸呈显著正相关，与 drafted whelk Hinia reticulata 和海螺 Buccinum undatum 的最大尺寸呈显著正相关。砂囊质量也与 drafted whelk 和海螺的最大尺寸呈显著正相关。喙体积和体重与 9 种食物中任何一种的大小均无显著相关性。对器官效应大小的分析表明，头体积与猎物大小呈正相关，而喙体积、砂囊质量和体重则没有显示出显著的正相关关系。这些结果表明，与脑质量相关的认知过程可能参与了绒鸭对猎物大小的选择。
