Houpt, Noah – Foraging Behaviours and Distribution of Four Avian predators of the Plainfin Midshipman (Porichthys notatus) (James Quinn and Sigal Balshine)

Acquiring resources is necessary for survival and reproduction in all known forms of life. When important resources are transiently available, the pressure to acquire them in an efficient way is even stronger due to time constraints, but this is poorly understood. The plainfin midshipman (Porichthys notatus) is a species of intertidally breeding fish which serves as a seasonally and diurnally transient resource for four avian piscivore species along the Pacific coast of North America. Descriptions of the foraging strategies employed by these predators to capture midshipman would provide insight into how predators take advantage of transiently available resources. The behaviours employed by bald eagles (Haliaeetus leucocephalus), glaucous-winged gulls (Larus glaucescens), great blue herons (Ardea herodias), and northwestern crows (Corvus caurinus) to capture and consume plainfin midshipman are described here. Additionally, bird census data are provided to describe how the distribution of these four predators relates to the availability of the midshipman fish. I found that bald eagles and great blue herons showed significantly higher abundance when the tide was receding than when it was incoming. Additionally, I found that glaucous-winged gull abundance in the intertidal zone decreased over time throughout the midshipman breeding season. The behavioural descriptions provide insight into the foraging strategies employed by four avian piscivores to take advantage of the transiently available resource of the midshipman fish. The bird census data provide some evidence that bald eagles, great blue herons, and glaucous-winged gulls distribute themselves spatio-temporally to take advantage of the transiently available midshipman fish.