Survivorship across the annual cycle of a migratory passerine, the willow flycatcher

Journal of Avian Biology
By: , and 



Annual survivorship in migratory birds is a product of survival across the different periods of the annual cycle (i.e. breeding, wintering, and migration), and may vary substantially among these periods. Determining which periods have the highest mortality, and thus are potentially limiting a population, is important especially for species of conservation concern. To estimate survival probabilities of the willow flycatcher Empidonax traillii in each of the different periods, we combined demographic data from a 10-year breeding season study with that from a 5-year wintering grounds study. Estimates of annual apparent survival for breeding and wintering periods were nearly identical (65–66%), as were estimates of monthly apparent survival for both breeding and wintering stationary periods (98–99%). Because flycatchers spend at least half the year on the wintering grounds, overall apparent survivorship was lower (88%) on the wintering grounds than on the breeding grounds (97%). The migratory period had the highest mortality rate, accounting for 62% of the estimated annual mortality even though it comprises only one quarter or less of the annual cycle. The migratory period in the willow flycatcher and many other neotropical migrants is poorly understood, and further research is needed to identify sources of mortality during this crucial period.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Survivorship across the annual cycle of a migratory passerine, the willow flycatcher
Series title Journal of Avian Biology
DOI 10.1111/jav.01371
Volume 48
Issue 8
Year Published 2017
Language English
Publisher Wiley
Contributing office(s) Pacific Island Ecosystems Research Center
Description 6 p.
First page 1126
Last page 1131