Interactive effects of senescence and natural disturbance on the annual survival probabilities of snail kites

Oikos
US Army Corps of Engineers; US Fish and Wildlife Service; St Johns River Water Management District; USGS
By: , and 

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Abstract

Individuals in wild populations face risks associated with both intrinsic (i.e. aging) and external (i.e. environmental) sources of mortality. Condition-dependent mortality occurs when there is an interaction between such factors; however, few studies have clearly demonstrated condition-dependent mortality and some have even argued that condition-dependent mortality does not occur in wild avian populations. Using large sample sizes (2084 individuals, 3746 re-sights) of individual-based longitudinal data collected over a 33 year period (1976-2008) on multiple cohorts, we used a capture-mark-recapture framework to model age-dependent survival in the snail kite Rostrhamus sociabilis plumbeus population in Florida. Adding to the growing amount of evidence for actuarial senescence in wild populations, we found evidence of senescent declines in survival probabilities in adult kites. We also tested the hypothesis that older kites experienced condition-dependent mortality during a range-wide drought event (2000-2002). The results provide convincing evidence that the annual survival probability of senescent kites was disproportionately affected by the drought relative to the survival probability of prime-aged adults. To our knowledge, this is the first evidence of condition-dependent mortality to be demonstrated in a wild avian population, a finding which challenges recent conclusions drawn in the literature. Our study suggests that senescence and condition-dependent mortality can affect the demography of wild avian populations. Accounting for these sources of variation may be particularly important to appropriately compute estimates of population growth rate, and probabilities of quasi-extinctions.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Interactive effects of senescence and natural disturbance on the annual survival probabilities of snail kites
Series title Oikos
DOI 10.1111/j.1600-0706.2010.18366.x
Volume 119
Issue 6
Year Published 2010
Language English
Publisher Scandinavian Society Oikos
Publisher location Copenhagen
Contributing office(s) Coop Res Unit Atlanta
Description 8 p.
First page 972
Last page 979
Online Only (Y/N) N
Additional Online Files (Y/N) N