Factors influencing subcolony colonization and persistence in a colonial seabird, the common murre Uria aalge

Abstract

Within an established seabird colony the choice of where to settle can be influenced by site fidelity, natal philopatry or public information. To form a new colony individuals must choose before philopatry has been established or public information is available. We explored the intracolony dynamics of common murres Uria aalge, specifically the formation and persistence of new subcolonies within a larger colony complex composed of numerous contiguous groups. We investigated the effects of (1) environmental conditions that influence the prey base, (2) predator disturbance, and (3) population size change on colonization patterns and modeled the persistence of recently colonized murre subcolonies as a function of their starting population sizes. Marine environmental conditions in the 2 winters previous to the breeding season had more influence than demographic and predator factors on whether subcolony colonizations occurred. The number of murres in the first year of colonization helped to explain the persistence of the subcolony, regardless of the amount of available nesting habitat within a subcolony area. Subcolonies that started out larger were more likely to persist. The results support the theory that the proportion of the entire murre population that attempts to breed in a given year is higher in years with favorable environmental conditions prior to the breeding season. Increased knowledge of murre colony formation may help scientists and managers understand the potential for recolonizations after colony extirpations or better predict the success of management actions such as social attraction or habitat modification.

Trade-offs in prey quality and quantity revealed through the behavioral compensation of breeding seabirds

“…Several indices were averaged across 2 seasonal periods each year: spring (March to May) and summer (June to August). This measure of spring captures the time period when seasonal upwelling begins in the Pacific Northwest (Holt & Mantua 2009), and is also the period when adult murres are returning to breeding colonies in Washington (Zador et al 2009). The summer period captures the entirety of the murre breeding period on Tatoosh (Zador et al 2009).…”

“…To test these hypotheses we used a 14 yr chick diet data set from common murres Uria aalge (hereafter: murres) nesting on Tatoosh Island, Washington State, USA (48°23.5' N, 124°44.2' W), a collection of rocky islets (total land area about 6 ha; Paine et al 1990) approximately 0.6 km off the tip of the Olympic Peninsula (Zador et al 2009). The island sits at the mouth of the Strait of Juan de Fuca, a region with a complex prey field (Brodeur et al 2005, Emmett et al 2006) and high variability in ocean productivity (Hickey 1998, Hickey & Banas 2003.…”

Storms and heat limit the nest success of Bank Cormorants: implications of future climate change for a surface-nesting seabird in southern Africa

“…AIC) to select between models (e.g. Wolfaardt et al 2008;Zador et al 2009). As Bank Cormorants are easily disturbed and displaced from their nests (Crawford and Cooper 2005), it was not always possible to record the number of eggs present on every check.…”

“…An exponential error distribution was employed to estimate the survival distribution as this assumes that nests fail at random through time (Zador et al 2009). Data were considered right censored if the nest persisted through the end of the study period.…”

Research priorities for seabirds: improving conservation and management in the 21st century

“…It is not clear whether these declines occurred despite increased recruitment from other colonies. This suggests that meta-population and source-sink dynamics will become increasingly important features of seabird conservation efforts in the future (Lebreton et al 2003, Zador et al 2009). …”