Data from: Influence of mate and nest-site fidelity on a declining, urban avian population

As urbanization reduces species’ habitats and population sizes, managers
need information on whether within-population processes, such as changes
in mate and nest-site fidelity and dispersal distances, may be
contributing to declines. We investigated whether mate fidelity, nest-site
fidelity, or breeding dispersal distance changed over time in a population
of burrowing owls (Athene cunicularia), a short-lived, socially-monogamous
species. During the 18-year period of the study, the population declined
by 69% in urban Santa Clara County, California, USA--a region of rapid
urbanization. We assessed whether these behaviors were influenced by key
factors including age, breeding success in the previous year, and years
with the same mate, and examined the relationship between mate and
nest-site fidelity over time and annual reproductive success. To evaluate
the relationship between mate and nest-site fidelity as well as overall
mate and nest-site fidelity rates by sex, we used Chi-Square tests. For
all other tests, we used Generalized Linear Mixed Models (GLMM) with
individual bird identification as a random variable to address the
inclusion of the same birds in multiple years. Our analyses showed no
change over time in mate fidelity, nest-site fidelity rates, dispersal
distances, or annual reproductive success, indicating these behaviors
remained stable even during a severe population decline. Although
burrowing owls are a short-lived species, we found that increasing years
with the same mate resulted in increased mate fidelity, nest-site
fidelity, and annual reproductive success. Since these fidelity behaviors
were maintained during the population decline, other factors require
investigation to determine the causes for decreases in numbers in this
population. Thus, even species such as burrowing owls, which can maintain
important fidelity behaviors in urban setting, are still subject to other
pressures that can cause population declines.