Divorce in cooperatively breeding long-tailed tits: a consequence of inbreeding avoidance?

The decision of whether to divorce a breeding partner between reproductive attempts can significantly affect individual fitness. In this paper, we report that 63% of surviving pairs of long-tailed tits Aegithalos caudatus divorced between years. We examine three likely explanations for the high divorce rate in this cooperative breeder. The 'better option' hypothesis predicts that divorce and re-pairing increases an individual's reproductive success. However, divorcees did not secure better partners or more helpers and there was no improvement in their reproductive success following divorce. The 'inbreeding avoidance' hypothesis predicts that females should disperse from their family group to avoid breeding with philopatric sons. The observed pattern of divorce was consistent with this hypothesis because, in contrast to the usual avian pattern, divorce was typical for successful pairs (81%) and less frequent in unsuccessful pairs (36-43%). The 'forced divorce' hypothesis predicts that divorce increases as the number of competitors increases. The pattern of divorce among failed breeders was consistent with this hypothesis, but it fails to explain the overall occurrence of divorce because divorcees rarely re-paired with their partners' closest competitors. We discuss long-tailed tits' unique association between divorce and reproductive success in the context of dispersal strategies for inbreeding avoidance

Experimental evidence for kin-biased helping in a cooperatively breeding vertebrate

The widespread belief that kin selection is necessary for the evolution of cooperative breeding in vertebrates has recently been questioned. These doubts have primarily arisen because of the paucity of unequivocal evidence for kin preferences in cooperative behaviour. Using the cooperative breeding system of long-tailed tits (Aegithalos caudatus) in which kin and non-kin breed within each social unit and helpers are failed breeders, we investigated whether helpers preferentially direct their care towards kin following breeding failure. First, using observational data, we show that not all failed breeders actually become helpers, but that those that do help usually do so at the nest of a close relative. Second, we confirm the importance of kinship for helping in this species by conducting a choice experiment. We show that potential helpers do not become helpers in the absence of close kin and, when given a choice between helping equidistant broods belonging to kin and non-kin within the same social unit, virtually all helped at the nest of kin. This study provides strong evidence that kinship plays an essential role in the maintenance of cooperative breeding in this species

Coordinated parental provisioning is related to feeding rate and reproductive success in a songbird

In species with biparental care, there is sexual conflict over parental investment because each parent benefits when their partner bears more of the reproductive costs. Such conflict can be costly for offspring, but recent theoretical work predicts that parents can resolve sexual conflict through behavioral negotiation, specifically by alternating their trips to provision nestlings. However, this idea has received almost no empirical attention. In this study, we test the hypothesis that parents alternate their delivery of food to offspring in long-tailed tits (Aegithalos caudatus) and investigate whether this coordination of parental care is associated with greater reproductive success. We show that parents alternate provisioning trips more than would be expected by chance and that parental alternation is repeatable across multiple observation periods at a nest. More alternation is associated with increased visit synchrony and increased food delivery to nestlings. Moreover, we found that nests with more alternation were less likely to be predated, probably resulting from reduced activity around the nest when parents coordinate their provisioning behavior. Our results support the hypothesis that alternation of offspring provisioning is a behavioral adaptation to reduce the costs of sexual conflict

Human MLPA Probe Design (H-MAPD): a probe design tool for both electrophoresis-based and bead-coupled human multiplex ligation-dependent probe amplification assays

<p>Abstract</p> <p>Background</p> <p>Multiplex ligation-dependent probe amplification (MLPA) is an efficient and reliable technique for gene dosage analysis. Currently MLPA can be conducted on two platforms: traditional electrophoresis-based, and FlexMAP bead-coupled. Since its introduction in 2002, MLPA has been rapidly adopted in both clinical and research situations. However, MLPA probe design is a time consuming process requiring many steps that address multiple criteria. There exist only one or two commercial software packages for traditional electrophoresis-based MLPA probe design. To our knowledge, no software is yet available that performs bead-coupled MLPA probe design.</p> <p>Results</p> <p>We have developed H-MAPD, a web-based tool that automates the generation and selection of probes for human genomic MLPA. The software performs physical-chemical property tests using UNAFold software, and uniqueness tests using the UCSC genome browser. H-MAPD supports both traditional electrophoresis-based assays, as well as FlexMAP bead-coupled MLPA.</p> <p>Conclusion</p> <p>H-MAPD greatly reduces the efforts for human genomic MLPA probe design. The software is written in Perl-CGI, hosted on a Linux server, and is freely available to non-commercial users.</p

Incubation in a temperate passerine: do environmental conditions affect incubation period duration and hatching success?

The timing of breeding often has a profound influence on the reproductive success of birds living in seasonal environments with rapidly changing nestling food availability. Timing is typically investigated with reference to lay dates, but it is the time of hatching that determines the ambient conditions and food availability that nestlings experience. Thus, in addition to lay date, phenological studies may also have to take account of variation in the length of the incubation period, which is likely to depend on both environmental conditions and parental traits. The primary aim of this study was to use a 24-year dataset to investigate the abiotic and biotic factors influencing variation in incubation duration in long-tailed tits (Aegithalos caudatus), a species in which incubation duration varies substantially (range: 12–26 days). We found support for our predictions that drier conditions, later breeding attempts and larger clutches were associated with shorter incubation periods. Larger clutches were also more resilient to increases in incubation duration associated with wet conditions. Surprisingly, warmer ambient conditions were associated with longer incubation periods. Secondly, we assessed the consequences of variation in the length of incubation periods for the risk of nest predation and the hatching success of surviving clutches. We show that longer incubation periods are likely to be costly due to increased exposure to nest predators. In contrast, we found only marginal effects of environmental conditions or incubation duration on hatching success, implying that wet conditions cause slower embryo growth and hence longer incubation periods, rather than causing embryo fatality. We suggest that long-tailed tits’ nests and parental behavior protect eggs from mortality arising directly from adverse weather conditions

Kith or Kin? Familiarity as a Cue to Kinship in Social Birds

© Copyright © 2020 Leedale, Li and Hatchwell. Interacting with relatives provides opportunities for fitness benefits via kin-selected cooperation, but also creates potential costs through kin competition and inbreeding. Therefore, a mechanism for the discrimination of kin from non-kin is likely to be critical for individuals of many social species to maximize their inclusive fitness. Evidence suggests that genetic cues to kinship are rare and that learned or environmental cues offer a more parsimonious explanation for kin recognition in most contexts. This is particularly true among cooperatively breeding birds, where recognition of familiar individuals is usually regarded as the most plausible mechanism for kin discrimination. In this article, we first review the evidence that familiarity provides an effective decision rule for discrimination of kin from non-kin in social birds. We then consider some of the complexities of familiarity as a cue to kinship, especially the problems of how individuals become familiar, and how familiar individuals are recognized. We conclude that while familiarity as a mechanism for kin recognition may be more parsimonious and widespread than genetic mechanisms, its apparent simplicity as a decision rule governing social interactions may be deceptive. Finally, we identify directions for future research on familiarity as a kin recognition mechanism in social birds and other taxa

Sex Allocation Patterns across Cooperatively Breeding Birds Do Not Support Predictions of the Repayment Hypothesis

The repayment hypothesis predicts that reproductive females in cooperative breeding systems overproduce the helping sex. Thanks to well-documented examples of this predicted sex ratio bias, repayment has been considered an important driver of variation in sex allocation patterns. Here we test this hypothesis using data on population brood sex ratios and facultative sex allocation from 28 cooperatively breeding bird species. We find that biased sex ratios of helpers do not correlate with production biases in brood sex ratios, contrary to predictions. We also test whether females facultatively produce the helping sex in response to a deficiency of help (i.e., when they have fewer or no helpers). Although this is observed in a few species, it is not a significant trend overall, with a mean effect size close to zero. We conclude that, surprisingly, repayment does not appear to be a widespread influence on sex ratios in cooperatively breeding birds. We discuss possible explanations for our results and encourage further examination of the repayment model

Social dynamics in nonbreeding flocks of a cooperatively breeding bird: causes and consequences of kin associations

Kin selection is regarded as a key process in the evolution of avian cooperative breeding, and kinship influences helper decisions in many species. However, the effect of kinship on nonbreeding social organization is still poorly understood despite its potential fitness implications. Here, we investigated the origins and consequences of kin associations in nonbreeding flocks of long-tailed tits, Aegithalos caudatus, an atypical cooperative breeder where helpers are failed breeders that redirect care towards relatives living in kin neighbourhoods. We found that kinship is an important factor in initial grouping decisions; all members of a nuclear family initially joined the same flock and failed breeders chose to flock with their relatives. Flocks that merged during the nonbreeding season also contained relatives. In contrast to these findings of positive kin association, when long-tailed tits switched flocks they tended to disperse into flocks with fewer relatives, although such switches often occurred with kin. In a playback experiment, we found no evidence that aggression shown towards members of other flocks was affected by kinship, indicating that kin associations result from a preference to flock with relatives rather than a constraint on flocking with nonrelatives. Finally, using social network analysis, we show that fine-scale nonbreeding associations among individuals were positively related to kinship, and that these nonbreeding associations were reflected in helping decisions in the subsequent breeding season, in addition to the previously reported effects of kinship and proximity. We conclude that long-tailed tits prefer to associate with kin when not breeding, and suggest that by doing so they gain either nepotistic benefits within flocks or future indirect benefits during breeding