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A recently favored hypothesis is that duetting in birds has a mate-guarding function: a male responds vocally to his partner’s
song, thereby forming a duet that repels males who are attracted to her song. Previous studies have not provided unambiguous
tests of the mate-guarding hypothesis because: (1) the probability of a male answering his partner’s song has not been shown
to increase specifically when the female is fertile, and (2) the probability of a male answering his partner’s song has not
been assessed separately from simply a higher song initiation rate. We investigated extra-pair paternity, mate-guarding, and
duetting in the socially monogamous Australian magpie-lark (Grallina cyanoleuca). DNA fingerprinting revealed that 3% of young were the result of extra-pair paternity, and we found that males guarded fertile
females by staying close to them. However, males did not initiate songs at a higher rate when females were fertile and actually
reduced their probability of replying to female song during this period. We conclude that although male magpie-larks did guard
fertile females in an attempt to prevent extra-pair copulations, they did not use duetting for this purpose.
Received: 10 May 1999 / Received in revised form: 27 September 1999 / Accepted: 2 October 1999 相似文献
2.
Subordinate males are more likely to help if unrelated to the breeding female in cooperatively breeding white-browed scrubwrens 总被引:2,自引:0,他引:2
Subordinates in communally breeding groups of birds usually help to provision nestlings, but in some species helping-at-the-nest
is facultative. In species in which groups usually contain relatives, subordinates either always feed young or are more likely
to do so when breeding dominants are close relatives, suggesting that benefits of helping collateral kin are important. In
other species, adult group members are unrelated to each other and males may only feed young if they have gained paternity,
showing that cooperation is related to the mating system. The white-browed scrubwren, Sericornis frontalis, is a communally breeding species in which most groups consist of a simple pair or a dominant pair with a subordinate male.
Subordinate males either fed nestlings in a given nest at a rate comparable to the dominants, or did not feed them at all.
Breeding groups usually formed through natal philopatry of males, so that about 80% of subordinates were closely related to
one or both members of the dominant pair. However, because of death and dispersal, 54% of subordinates were unrelated to the
resident female. Although subordinates with their mother fed nestlings in 48% of cases, they fed offspring in 75% of cases
if their mother had been replaced by an unrelated female, suggesting that their decision to help is influenced by the opportunity
to mate with the female. Supporting this conclusion, relatedness to the dominant male did not affect subordinate behaviour,
and genetic studies showed that subordinates often gained paternity if unrelated to the female. Thus, paradoxically, provisioning
nestlings is related to the opportunity for mating in a society in which there is natal philopatry and subordinates are usually
related to one or both members of the dominant pair.
Received: 25 January 1997 / Accepted after revision: 1 May 1997 相似文献
3.
John Magrath 《Local Environment》2013,18(9-10):891-901
Farmers and pastoralists in Africa are remarkably consistent across countries in how they report climate is changing. These changes are still relatively small but, combined with the effects of chronic poverty, disease and environmental degradation, are already having severe human consequences. The changes are consistent with what is expected to occur due to man-made global warming and will increase. Women are especially impacted. Africa is least responsible for greenhouse gas emissions, but will suffer some of the most damaging consequences. Adaptation is essential. This will require finance from international sources. However, there is much African governments can and should do to start. Boosting adaptation to current climatic variability and shocks and tackling poverty will bring benefits today and for the future. 相似文献
4.
Michael J. L. Magrath Peter Santema Karen M. Bouwman Dušan M. Brinkhuizen Simon C. Griffith Naomi E. Langmore 《Behavioral ecology and sociobiology》2009,63(5):661-672
Reproductive success within populations often varies with the timing of breeding, typically declining over the season. This
variation is usually attributed to seasonal changes in resource availability and/or differences in the quality or experience
of breeders. In colonial species, the timing of breeding may be of particular importance because the costs and benefits of
colonial breeding are likely to vary over the season and also with colony size. In this study, we examine the relationship
between timing of breeding and reproductive performance (clutch size and nest success) both within and between variable sized
colonies (n = 18) of fairy martins, Petrochelidon ariel. In four of these colonies, we also experimentally delayed laying in selected nests to disentangle the effects of laying
date and individual quality/experience on reproductive success. Within colonies, later laying birds produced smaller clutches,
but only in larger colonies. The general seasonal decline in nest success was also more pronounced in larger colonies. Late
laying birds were generally smaller than earlier laying birds, but morphological differences were also related to colony size,
suggesting optimal colony size also varies with phenotype. Experimentally delayed clutches were larger than concurrently produced
non-delayed clutches, but only in larger colonies. Similarly, delayed clutches were more likely to produce fledglings, particularly
later in the season and in larger colonies. We suggest that the reduced performance of late breeding pairs in larger colonies
resulted primarily from inexperienced/low quality birds preferring to settle in larger colonies, possibly exacerbated by an
increase in the costs of coloniality (e.g., resource depletion and ectoparasite infestations) with date and colony size. These
findings highlight the importance of phenotype-related differences in settlement decisions and reproductive performance to
an improved understanding of colonial breeding and variation in colony size. 相似文献
5.
Sally Rangecroft Stephan Harrison Karen Anderson John Magrath Ana Paola Castel Paula Pacheco 《Ambio》2013,42(7):852-863
Climate change is projected to have a strongly negative effect on water supplies in the arid mountains of South America, significantly impacting millions of people. As one of the poorest countries in the region, Bolivia is particularly vulnerable to such changes due to its limited capacity to adapt. Water security is threatened further by glacial recession with Bolivian glaciers losing nearly half their ice mass over the past 50 years raising serious water management concerns. This review examines current trends in water availability and glacier melt in the Bolivian Andes, assesses the driving factors of reduced water availability and identifies key gaps in our knowledge of the Andean cryosphere. The lack of research regarding permafrost water sources in the Bolivian Andes is addressed, with focus on the potential contribution to mountain water supplies provided by rock glaciers. 相似文献
6.
Vedder O Magrath MJ Niehoff DL van der Velde M Komdeur J 《Behavioral ecology and sociobiology》2012,66(4):603-612
Although functional explanations for female engagement in extra-pair copulation have been studied extensively in birds, little
is known about how extra-pair paternity is linked to other fundamental aspects of avian reproduction. However, recent studies
indicate that the occurrence of extra-pair offspring may generally decline with laying order, possibly because stimulation
by eggs induces incubation, which may suppress female motivation to acquire extra-pair paternity. Here we tested whether experimental
inhibition of incubation during the laying phase, induced by the temporary removal of eggs, resulted in increased extra-pair
paternity, in concert with a later cessation of laying, in blue tits (Cyanistes caeruleus). As expected, experimental females showed a more gradual increase in nocturnal incubation duration over the laying phase
and produced larger clutches than controls. Moreover, incubation duration on the night after the first egg was laid predicted
how extra-pair paternity declined with laying order, with less incubation being associated with more extra-pair offspring
among the earliest eggs in the clutch. However, incubation duration on this first night was unrelated to our experimental
treatment and independent of final clutch size. Consequently, the observed decline in extra-pair paternity with laying order
was unaffected by our manipulation and larger clutches included proportionally fewer extra-pair offspring. We suggest that
female physiological state prior to laying, associated with incubation at the onset of laying, determines motivation to acquire
extra-pair paternity independent of final clutch size. This decline in proportion of extra-pair offspring with clutch size
may be a general pattern within bird species. 相似文献
7.
Relatedness, polyandry and extra-group paternity in the cooperatively-breeding white-browed scrubwren (Sericornis frontalis ) 总被引:3,自引:0,他引:3
Linda A. Whittingham Peter O. Dunn Robert D. Magrath 《Behavioral ecology and sociobiology》1997,40(4):261-270
We used DNA fingerprinting to examine the genetic parentage and mating system of the cooperatively breeding white-browed
scrubwren, Sericornis frontalis, in Canberra, Australia. Our analyses revealed a remarkable variety of mating tactics and social organization. Scrubwrens
bred in pairs or multi-male groups that consisted of a female and two or more males. Females were always unrelated to the
pair male or alpha (dominant) male. Among multi-male groups we found three different mating tactics. Firstly, when alpha and
beta (subordinate) males were unrelated, they usually shared paternity in the brood. This resulted in both males gaining reproductive
benefits directly. Secondly, when beta males were not related to the female but were related to the alpha males, beta males
sired offspring in some broods. In this situation, beta males gained reproductive benefits both directly and potentially indirectly
(through the related alpha male). Thirdly, when beta males were related to the female or both the female and alpha male, they
remained on their natal territory and did not sire any offspring. Thus beta males gained only indirect reproductive benefits.
Overall, when group members were related closely, the dominant male monopolized reproductive success, whereas when the members
were not related closely the two males shared paternity equally. This positive association between monopolization of reproduction
and relatedness is predicted by models of reproductive skew, but has not been reported previously within a single population
of birds. Other cooperatively breeding birds with both closely related and unrelated helpers may show a similar variety of
mating tactics. Finally, we found that extra-group paternity was more common in pairs (24% of young) than in multi-male groups
(6%), and we discuss three possible reasons for this difference.
Received: 21 May 1996 / Accepted after revision: 14 December 1996 相似文献
8.
Vedder O Komdeur J van der Velde M Schut E Magrath MJ 《Behavioral ecology and sociobiology》2011,65(4):741-752
Polygyny and extra-pair paternity are generally thought to enhance sexual selection. However, the extent to which these phenomena
increase variance in male reproductive success will depend on the covariance between success at these two strategies. We analysed
these patterns over four breeding seasons in facultatively polygynous blue tits Cyanistes caeruleus. We found that both polygyny and extra-pair paternity increased variance in male reproductive success and that standardised
variance in annual number of genetic fledglings was 2.6 times higher than standardised variance in apparent success when assuming
strict monogamy. Nevertheless, male success at securing within-pair paternity was unrelated to success at gaining extra-pair
paternity and, when considering the positive effect of age on extra-pair success and attracting a second female, polygynous
males were no more likely to sire extra-pair fledglings. Overall, polygynous males fledged more genetic offspring than monogamous
males, but first-year polygynous males lost a greater share of within-pair paternity. A literature review suggests that this
adverse effect of polygyny on within-pair paternity is frequent among birds, inconsistent with the prediction that females
engage in extra-pair copulation with successful males to obtain good genes. Furthermore, a male's share of paternity was repeatable
between years, and among females of polygynous males within years, such that a compatibility function of extra-pair copulations
was likewise unsupported. Instead, we suggest that the observed patterns are most consistent with a fertility insurance role
for extra-pair copulations, which does not exclude the greater opportunity for sexual selection through differential ability
of males to gain paternity. 相似文献
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