Dispersal and recruitment during population growth in a colonial bird, the great cormorantPhalacrocorax carbo sinensis

Abstract

While the factors influencing reproduction and survival in colonial populations are relatively well studied, factors involved in dispersal and settlement decisions are not well understood. The present study investigated exchanges of great cormorants Phalacrocorax carbo sinensis among six breeding colonies over a 13‐year period when the breeding population in Denmark increased from 2800 to 36 400 nests. We used a multistate capture‐recapture model that combined multisite resightings and recoveries to examine simultaneously recruitment, natal dispersal, breeding dispersal and annual survival of first‐year, immature and breeding great cormorants. Mean survival of first‐year birds (0.50±0.09, range=0.42–0.66 among colonies) was lower than survival of breeders (0.90±0.06, range=0.81–0.97). Mean survival of immature birds over the study period was 0.87±0.08. Dispersal from a colony increased with decreasing mean brood size in the colony in both first‐time and experienced breeders. The choice of the settlement colony in first‐time breeders was affected by conditions in the natal colony and in the colonies prospected during the pre‐breeding years. In particular, first‐time breeders recruited to colonies where they could expect better breeding success. Experienced breeders relied mainly on cues present early in the season and on their own breeding experience to choose a new breeding colony. Newly established colonies resulted mainly from the immigration of first‐time breeders originating from denser colonies. Dispersal was distance‐dependent and first‐time breeders dispersed longer distances than breeders. We suggest that the prospecting behaviour allows first‐time breeders to recruit in nearby as well as more distant potential breeding colonies. Dispersing breeders preferred to settle in neighbouring colonies likely to benefit from their experience with foraging areas. We discuss the importance of these movements for growth and expansion of the breeding population.

Dispersal of the White Stork Ciconia ciconia in the Lonjsko polje Nature Park, Croatia

“…The distance of reproductive dispersion in this study was 4.6 km, which is close to main natal dispersion in this study (4.21 km). Results from other research have also shown that natal dispersion is more common and individuals travel larger distances when compared to reproductive dispersion (Vergara et al 2006, Hénaux et al 2007, Itonaga 2009.…”

Towards optimized population control efficiency in space and time: A modelling framework adapted to a colonial waterbird

“…However, our modelling framework is flexible enough to allow additional sophistication of the model as well as more complex, real-life scenarios to be investigated in the future. For instance, future versions of the model could accommodate the possibility of density-dependent survival (Frederiksen and Bregnballe, 2000; but see also Frederiksen et al, 2001) and the possibility that cormorants, particularly first-time breeders, use public information to select a breeding colony (Henaux et al, 2007). More realistic scenarios may include irregular spatial grids with unequal spacing between active colonies, and the fact that different colonies may have different carrying capacities and/or be at different stages of their dynamics.…”

“…Specifically, our aims were as follows: (i) to present a deterministic stage-structured metapopulation model parameterized for the cormorant. Our model represents a step beyond the works of Blackwell et al (2002) who developed a single population model and Duerr (2007) whose metapopulation model, parameterized for cormorant colonies in the Lake Champlain, lacked an explicit spatial context which is necessary to accommodate distance-dependent dispersal as evidenced in the closely related great cormorant (Henaux et al, 2007); (ii) as our model was designed to be an effective strategic and management decision tool, we also developed simulation tools to gain insight into the efficiency gain that could be expected from a better coordination of management activities in space and time; (iii) our modelling framework was applied to a case study in which we investigated the relative importance of the spatiotemporal location and degree of clustering of specific management activities on management efficiency.…”

“…Although estimates available in the literature may not be generally applicable, as dispersal is a complex trait conditional on the interaction of individual, social and environmental causes (Martin et al, 2008), we used dispersal estimates described by Duerr (2007) and by Henaux et al (2007) for the great cormorant as our references.…”

Visitor noise at a nesting colony alters the behavior of a coastal seabird

“…social information; Schjørring et al 2000, Hénaux et al 2007). Moreover, experience and familiarity of a nesting site is related to higher reproductive success, where knowing your neighbors decreases territorial aggression and knowledge of nearby feeding grounds makes foraging more efficient (Piper 2011).…”