Influence of density‐dependent competition on foraging and migratory behavior of a subtropical colonial seabird

Abstract

Density‐dependent competition for food resources influences both foraging ecology and reproduction in a variety of animals. The relationship between colony size, local prey depletion, and reproductive output in colonial central‐place foragers has been extensively studied in seabirds; however, most studies have focused on effects of intraspecific competition during the breeding season, while little is known about whether density‐dependent resource depletion influences individual migratory behavior outside the breeding season. Using breeding colony size as a surrogate for intraspecific resource competition, we tested for effects of colony size on breeding home range, nestling health, and migratory patterns of a nearshore colonial seabird, the brown pelican (Pelecanus occidentalis), originating from seven breeding colonies of varying sizes in the subtropical northern Gulf of Mexico. We found evidence for density‐dependent effects on foraging behavior during the breeding season, as individual foraging areas increased linearly with the number of breeding pairs per colony. Contrary to our predictions, however, nestlings from more numerous colonies with larger foraging ranges did not experience either decreased condition or increased stress. During nonbreeding, individuals from larger colonies were more likely to migrate, and traveled longer distances, than individuals from smaller colonies, indicating that the influence of density‐dependent effects on distribution persists into the nonbreeding period. We also found significant effects of individual physical condition, particularly body size, on migratory behavior, which in combination with colony size suggesting that dominant individuals remain closer to breeding sites during winter. We conclude that density‐dependent competition may be an important driver of both the extent of foraging ranges and the degree of migration exhibited by brown pelicans. However, the effects of density‐dependent competition on breeding success and population regulation remain uncertain in this system.

Measuring ontogenetic shifts in central-place foraging insects: a case study with honey bees

“…While it is well established that recording the patterns of time-activity budgets in central-place foraging can provide information on foraging traits such as habitat use and diet (e.g. Lamb, Satgé, & Jodice, 2017; Briscoe et al, 2018), fewer studies have revealed their potential for analysing keystone ontogenetic traits (e.g. Lambin & Yoccoz, 2001; Gopukumar, 2003; Benton, St Clair, & Plaistow, 2008; Fay, Barbraud, Delord, & Weimerskirch, 2016).…”

“…However, bio-logging applications are still restricted to birds (particularly seabirds, e.g. Rishworth et al, 2014; Fay et al, 2016; Lamb et al, 2017), fishes (Gurarie et al, 2016) and mammals (Lambin & Yoccoz, 2001; Gopukumar, 2003; Gurarie, Andrews, & Laidre, 2009; Briscoe et al, 2018). Very few studies were conducted on insects (but see Degen et al, 2016 for bees), despite the recent availability of adapted miniaturized devices (Kissling, Pattemore, & Hagen, 2014; Nunes-Silva et al, 2019).…”

Residency, recruitment, and stopover duration of hatch-year Roseate Terns (Sterna dougallii) during the premigratory staging period

“…Additional work is needed to assess prey fish availability at colony sites throughout the breeding season and at Cape Cod staging areas to determine whether this hypothesis has support. Previous work in Brown Pelicans (Pelecanus occidentalis) has shown that density-dependent resource competition at breeding colonies can influence migratory behavior postbreeding (Lamb et al 2017).…”

“…This dearth of information is concerning considering that staging, migration, and wintering periods comprise the majority of the avian annual cycle, and conditions during these periods may have carryover effects that influence survival and reproduction in subsequent breeding seasons (Sorensen et al 2009, Harrison et al 2011, Salton et al 2015, Szostek and Becker 2015. Additionally, conditions during the breeding season, such as resource competition, may also influence migration strategies (Lamb et al 2017).…”

Causes and consequences of inverse density‐dependent territorial behaviour and aggression in a monogamous mammal

“…Population density is an important driver of many ecological processes and patterns, for example dispersal (Bowler & Benton, 2005;Maag, Cozzi, Clutton-Brock, & Ozgul, 2018), competition (Lamb, Satgé, & Jodice, 2017), sexual selection (Kokko & Rankin, 2006) and territoriality. Density dependence can be both positive and negative.…”