Do Birds Alter Levels of Parental Investment Based on Nest‐Site Habitat Features?

Abstract

Many habitats have undergone rapid changes over the past century as a result of anthropogenic activities. Organisms can respond to changes in their environment in many ways, including how much they invest in a given reproductive bout. Optimality theory and life history theory together have provided a framework for understanding how individuals make decisions about the risks and rewards of investing high levels of resources into their offspring within the context of current vs. future reproduction. Shrubland birds in the United States often breed in habitat that has been impacted by humans to varying degrees and provide an ideal system for examining whether organisms alter their levels of parental investment based on the habitat around the nest site. In this study, we assessed levels of nest‐defense behavior during a simulated nest predation event in four shrubland birds: American robins (Turdus migratorius), gray catbirds (Dumetella carolinensis), brown thrashers (Toxostoma rufum), and northern cardinals (Cardinalis cardinalis). We found that thrashers and catbirds exhibited significantly higher levels of nest defense compared to robins and cardinals and that birds with larger broods acted more aggressively in defending them. We also found that thrashers acted less aggressively as the proportion of shrubland around the nest increased and as the proportion of developed land around the nest decreased and that cardinals acted less aggressively as the proportion of developed land around the nest increased. These patterns suggest that nest‐defense behavior can covary with features of the landscape surrounding the nest, but that the factors shaping that behavior can differ by species.

Prevalence and consequences of ants and other arthropods in active nests of Midwestern birds

“…Bird nests at ten sites in Illinois were monitored from April through July of 2014 and May through July of 2015 as part of the experiments conducted by Merrill et al (2016) and were subsequently used in the current study (Supplemental Table 1). Bird nests were located by D r a f t systematically searching optimal nesting habitats at each study site, and by using targeted searches in areas where adult birds exhibited nesting behaviors, including alarm-calling.…”

Flexible nest‐site selection under anthropogenic habitat change in an Afrotropical understorey insectivore

“…Therefore, we here propose four mechanisms that should be taken into consideration by future studies of the breeding ecology of Placid Greenbuls and other tropical open-cup nesting passerines. First, parents may actively deter predators and thereby compensate for poor nest concealment, allowing successful breeding in predator-rich environments (Andersson et al 1980, Weidinger 2002, Remeš 2005, Merrill et al 2016. This may, in particular, be the case for cooperative breeders, where subordinates assist in protecting offspring against predators before and after fledging (Mumme 1992, Innes & Johnston 1996, Riehl & Jara 2009.…”