Markov chain estimation of avian seasonal fecundity

Authors

MATTHEW A. ETTERSON, U.S. Environmental Protection Agency
RICHARD S. BENNETT, U.S. Environmental Protection Agency
ERIC L. KERSHNER, U.S. Marine Corps Base Camp Pendleton
JEFFERY W. WALK, The Nature Conservancy

Document Type

Article

Date of this Version

6-12-2009

Citation

Ecological Applications, 19(3), 2009, pp. 622–630

Comments

This document is a U.S. government work and is not subject to copyright in the United States.

Abstract

Avian seasonal fecundity is of interest from evolutionary, ecological, and conservation perspectives. However, direct estimation of seasonal fecundity is difficult, especially with multi-brooded birds, and models representing the renesting and quitting processes are usually required. To explore the consequences of modeling decisions on inference about avian seasonal fecundity, we generalize previous Markov chain (MC) models of avian nest success to formulate two different MC models of avian seasonal fecundity that represent two different ways to model renesting decisions and breeding cessation. We parameterize both Markov chains (regular and absorbing) for two species (Eastern Meadowlark, Sturnella magna, and Dickcissel, Spiza americana) and compare the results using mean-square error of the estimated number of successful broods per breeding female. We also provide formulae for estimating the expected variation in female breeding success. The absorbing MC performed better for both species, although the regular MC performed almost as well when the duration of the breeding season was estimated by taking the 95th percentile of a negative binomial distribution fit to the observed durations among all females. In their simplest form the models contain very few parameters (four or five) and should also prove useful as a foundation for more complex models of avian seasonal fecundity and demography.