of the cumulative value of stimulation) on synchronization remains unclear. 2007) and provide evidence of the endocrine mechanisms of social stimulation ( Ball & Bentley 2000 Wingfield et al. Some empirical studies support these predictions (Waas et al. More synchronous breeding is thus expected under the stronger social stimulation occurring in larger colonies. In any case, these ultimate explanations cannot inform us about the proximate mechanisms leading to breeding synchrony in the first place, which are the focus of this paper.ĭarling (1938) proposed a proximate mechanism for synchrony: non-breeding birds in a colony are stimulated by the cumulative value of the voice, and the presence of the breeding members of the colony to start breeding themselves.
Coulson (2002) suggested that these advantages are consequences rather than (adaptive) causes of breeding synchrony. However, empirical tests of these hypotheses are inconclusive, suggesting that the advantages of synchronized breeding could either be case specific or occur in different combinations, or even that synchrony can be maladaptive ( Gochfeld 1980 Wittenberger & Hunt 1985). Different ultimate explanations of colony synchrony have been proposed, including predation satiation, mate finding, reduction of intraspecific interactions and formation of juvenile flocks ( Darling 1938 Emlen & Demong 1975 Yom-Tov 1975 Nelson 1980 Mougin et al. We argue that collective patterns such as breeding synchrony in colonial birds could have simple adaptive individual-level explanations.īreeding synchrony is a characteristic of colonial birds-female birds in a colony are often at a strikingly similar breeding stage: laying eggs incubating or feeding similarly aged chicks ( Gochfeld 1980 Nelson 1980 Coulson 2002). Our study highlights the power of local adaptive (individual) behaviour to create global (colony) patterns. Moreover, females bred in a safer environment, which is known from field studies to increase fitness. Even giving only a low relevance to the neighbour's stress level was enough to synchronize the laying date of neighbours and also of a huge colony. A female laid her eggs when her stress level fell to a critical value. We tested our hypotheses using a generic individual-based model where the breeding predisposition of females was updated daily depending on an increase in the photoperiod (positively) and the stress level of neighbours: negatively if they were agitated, and positively otherwise. Moreover, we propose that this local process, together with environmental cues, can synchronize breeding between neighbours and through a whole colony.
We propose that social tranquillity at the time of laying can be achieved if a bird's stress level is partly determined by the agitation of its neighbours. In colonies, conspecific birds often destroy eggs and kill chicks, either intentionally or not. This is the handful that actually are link commands.Why and how birds in colonies often breed in striking synchrony is an unsolved question. Here are the entries in the Dictionary under Linksīoth-ends clear-links create-from create-from create-to create-to create-with create-with create-link-from create-links-from create-link-to create-links-to create-link-with create-links-with die hide-link in-neighbor? in-neighbors in-from in-link-neighbor? in-link-neighbors in-link-from is-directed-link? is-link? is-link-set? is-undirected-link? layout-radial layout-spring layout-tutte -neighbor? -neighbors -with link-heading link-length link-neighbor? link links links-own -own link-neighbors link-with my- my-in- my-in-links my-links my-out- my-out-links no-links other-end out-neighbor? out-neighbors out-to out-link-neighbor? out-link-neighbors out-link-to show-link tie untie Most of them are turtle commands such asking the turtles to do something with their links or report something about their links. Links have several entries in the NetLogo dictionary, but only a few are used directly by links (i.e., ask links or ask link 4 5 ).
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