Importance of habitat saturation and territory quality for evolution of cooperative breeding in the Seychelles warbler

Abstract Within socially monogamous breeding systems, levels of extra-pair paternity can vary not only between species, populations, and individuals, but also across time. Uncovering how different extrinsic conditions (ecological, demographic, and social) influence this behavior will help shed light on the factors driving its evolution. Here, we simultaneously address multiple socio-ecological conditions potentially influencing female infidelity in a natural population of the cooperatively breeding Seychelles warbler, Acrocephalus sechellensis. Our contained study population has been monitored for more than 25 years, enabling us to capture variation in socio-ecological conditions between individuals and across time and to accurately assign parentage. We test hypotheses predicting the influence of territory quality, breeding density and synchrony, group size and composition (number and sex of subordinates), and inbreeding avoidance on female infidelity. We find that a larger group size promotes the likelihood of extra-pair paternity in offspring from both dominant and subordinate females, but this paternity is almost always gained by dominant males from outside the group (not by subordinate males within the group). Higher relatedness between a mother and the dominant male in her group also results in more extra-pair paternity—but only for subordinate females—and this does not prevent inbreeding occurring in this population. Our findings highlight the role of social conditions favoring infidelity and contribute toward understanding the evolution of this enigmatic behavior.

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Exploring territory quality in the North American red squirrel through removal experiments

Canadian Journal of Zoology ◽

10.1139/z95-133 ◽

1995 ◽

Vol 73 (6) ◽

pp. 1115-1122 ◽

Cited By ~ 32

Author(s):

Karl W. Larsen ◽

Stan Boutin

Keyword(s):

North American ◽

Poor Quality ◽

Tamiasciurus Hudsonicus ◽

Red Squirrel ◽

Territory Quality ◽

The North ◽

Removal Experiments ◽

Habitat Saturation ◽

Removal Studies ◽

North American Red Squirrel

If territory quality affects the fitness of its holder, then relatively unsuccessful individuals should relocate if given the opportunity to appropriate a higher quality territory. Relocation by these animals, however, may be prevented by habitat saturation, poor competitive ability, or the costs of relocating. We conducted two removal studies that created numerous territory vacancies in a population of the North American red squirrel (Tamiasciurus hudsonicus), thus providing favourable conditions for relocation. In both experiments, we tested whether nonbreeding females were more likely to relocate than breeding females, presumably because they (the nonbreeders) occupied relatively poor-quality territories. In our first experiment we permanently removed most of the squirrels from a study site and monitored the relative proportions of the remaining nonbreeding and breeding females that relocated. In our second experiment we monitored the response of squirrels to vacant territories that had been previously held by nonbreeding and breeding females, as well as by males. We also monitored the behaviour of squirrels that did not hold territories (dispersing offspring), as these individuals would not experience the same costs of relocation as adults. Our experiments showed that neither category of female was likely to relocate, regardless of the type of territory available. Both residents and dispersing offspring displayed no biases towards vacant territories that previously belonged to nonbreeding or breeding females or to males. Relocation does not appear to be a strategy for a female in this system to increase her reproductive opportunities. This suggests that either territory quality is inconsequential or the costs of relocation are prohibitive. Dispersing offspring also may be unable to select certain territories because of the premium placed on acquiring a territory, regardless of its quality.

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Inter-island transfers and population dynamics of Seychelles Warblers Acrocephalus sechellensis

Bird Conservation International ◽

10.1017/s0959270900001374 ◽

1997 ◽

Vol 7 (1) ◽

pp. 7-26 ◽

Cited By ~ 11

Author(s):

Jan Komdeur

Keyword(s):

Population Dynamics ◽

First Year ◽

Territory Quality ◽

Island Endemic ◽

Breeding Populations ◽

Suitable Space ◽

Seychelles Warbler ◽

Successful Establishment ◽

Term Management

SummaryIn the 1950s the Seychelles Warbler Acrocephalus sechellensis was a highly threatened single-island endemic species with a population of 26 individuals confined to Cousin Island in the inner Seychelles. Following long-term management of Cousin, the population steadily recovered to around 300–360 birds. In order to give the species the security of additional breeding populations, some warblers were successfully transferred to the islands of Aride and Cousine in September 1988 and June 1990 respectively. During the three years after the transfer to Aride and the first year after the transfer to Cousine, mean territory quality (measured as insect prey available) on these islands was significantly higher than that on Cousin, leading to higher reproductive success per territory and survival of juveniles and adult birds. In November 1991, all transferred birds were still alive, and 205 young had fledged successfully, bringing the total warbler population to c.585 birds. By then there was enough suitable space still remaining on Aride and Cousine for young birds to establish territories and the rise in warbler numbers is expected to continue. The successful establishment of three self-sustaining and viable breeding populations has ensured that the Seychelles Warbler is no longer a globally threatened species.

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Compensatory and additive helper effects in the cooperatively breeding Seychelles warbler (Acrocephalus sechellensis)

10.1101/372722 ◽

2018 ◽

Author(s):

Lotte A. van Boheemen ◽

Martijn Hammers ◽

Sjouke A. Kingma ◽

David S. Richardson ◽

Terry Burke ◽

...

Keyword(s):

Group Size ◽

Food Availability ◽

Dominant Male ◽

List Type ◽

Territory Quality ◽

Trade Offs ◽

Cooperatively Breeding ◽

Helping Behaviour ◽

Seychelles Warbler ◽

The Impact

ABSTRACTIn cooperatively breeding species, helper aid may affect dominant breeders’ investment trade-offs between current and future reproduction. By compensating for the care provided by helpers, breeders can reduce the costs of reproduction and improve chances of survival. Also, helper care can be additive to that of dominants, resulting in higher success of the current brood.However, the influence of helpers on offspring care itself may be the by-product of group size and territory quality. Therefore to make conclusive inferences about causation of additive and compensatory care as a result of helpper serequires disentangling the impact of helping from other factors determining parental investment.In this study, we use 20 years of offspring provisioning data to investigate the effect of helping on breeder and overall offspring provisioning rates in the facultative cooperatively breeding Seychelles warbler (Acrocephalus sechellensis). Our extensive dataset allowed us to effectively control for the effects of living in a larger group and in territories with higher food availability.We show compensatory and additive care in response to helper aid. Helpers lightened the provisioning load of the dominant male and female and increased the total provisioning to the nestlings. This was irrespective of group size or territory quality (food availability).Our results illustrate how multiple benefits of helping behaviour can simultaneously be fundamental to the evolutionary maintenance of cooperative behaviour.

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