Sex difference in criteria determining fidelity towards breeding sites in the great cormorant

Abstract

Summary1. Many animals choose to breed in sites where they have previously been successful. Such ®delity could arise from the predictability of high quality breeding sites in a temporally stable environment. The quality of a site may be indicated by factors other than an individual's own success, because it may fail as a result of a random event that is unrelated to the intrinsic quality of the site. In particular, prior experience (familiarity) with the breeding area and the performance of neighbours could give complementary information about the quality of the site. 2. We present results from a long-term study of colonial great cormorants (Phalacrocorax carbo sinensis), where movement and reproductive success of individually marked birds within a colony was known. 3. Individuals were more likely to return to the same breeding site if they had been successful the previous season. 4. Fidelity of both males and females increased with increasing level of familiarity with the breeding area. Males were more likely to breed again in the same area, and their ®delity was more dependent on familiarity with the area than female ®de-lity. 5. The success of breeding sites within the colony was spatially autocorrelated, and cueing on neighbour performance should thus be advantageous. Female ®delity increased with increasing success of neighbouring birds, while male ®delity was unaected by neighbour success. 6. We suggest that the dierence between the sexes in the criteria determining ®de-lity arises because it is mainly the males that are involved in territorial disputes. They may therefore bene®t more than females from knowing their neighbours, and this could override the importance of the intrinsic quality of the breeding area (i.e. reproductive success of neighbours). 7. The con¯ict over preferred breeding sites that arises within breeding pairs because of this sex dierence may be an explanation for the high rate of mate change between years (92.5%) observed in this species.

Nest fidelity is driven by multi-scale information in a long-lived seabird

“…Individual success does not influence the probability of dispersing for birds breeding on cliffs with high local reproductive success, whereas individual success is highly, negatively related to dispersal for birds breeding on cliffs with lower local reproductive success, suggesting that the information provided by the average success of conspecifics is sufficient to override individual or pair experience. Schjørring et al [39] found similar results in the great cormorant, Phalacrocorax carbo, in which the fidelity of females to their nesting site increases with both their own success and the increasing success of neighbouring pairs (BS was found to be spatially autocorrelated within the colony). Such double, hierarchical influence of social public and personal information on nesting site selection has been experimentally confirmed in a non-colonial short-lived passerine bird, the collared flycatcher, Ficedula albicollis [10].…”

Conspecific reproductive success affects age of recruitment in a great cormorant, Phalacrocorax carbo sinensis , colony

“…At present, we do not have the data to support or invalidate this hypothesis; however, the fact that our sample sizes of females and males were almost identical counts against it. SchjÖrring et al (2000) showed that female great cormorants are more likely than males to change nest site within the colony from year to year; this could contribute to an underestimation of the true sex di¡erence, since marked females would be more likely than males to have bred previously in unobserved parts of the colony. Overall, the results presented here indicate that male recruitment is constrained by the availability of females, and that not all males may be able to start breeding at the optimal time.…”

Is it always beneficial to breed in the centre? Trade-offs in nest site selection within the colony of a tree-nesting waterbird

“…Male Great Cormorants arrive at the colony first and establish territories that are subsequently assessed and selected by females (Schjørring et al 1999). Since older, high-quality males are expected to more reliably judge nest site quality, relying upon their prior experience (Schjørring et al 2000), they are likely to choose the best available sites and attract high-quality females. Preferences of high-quality pairs for central nesting site would be consistent with the central-periphery pattern of distribution, while selection according to physical quality would indicate the random model.…”