Incest avoidance, extrapair paternity, and territory quality drive divorce in a year-round territorial bird

Abstract

Divorce can be an important behavioral strategy to improve fitness. This is particularly relevant for species that are territorial yearround with continuous partnerships, where individuals face constraints on partner choice due to limited vacancies and dispersal opportunities. We tested several hypotheses for divorce in such a species, the cooperatively breeding bird Malurus coronatus. Based on 9 years of detailed information on dispersal and survival of 317 breeding pairs, we tested whether divorce is driven by inbreeding avoidance, by a better partner or territory, or by social variables (number of subordinates and fidelity of partners). We found that divorce is important to escape incest: incestuous pairs were substantially more likely to divorce (64%) than non-incestuous pairs (14%). However, incestuous pair bonds lasted up to a year, highlighting constraints on breeder dispersal. Non-incestuous pairs also divorced, but here the only predictor for divorce was the presence of extrapair offspring in a previous brood. Although reproductive failure did not trigger divorce, and reproductive success did not improve in the year following divorce, females that dispersed after divorce obtained higher quality territories, unlike females that dispersed after their partner died. Thus, divorce may be a strategy to improve long-term benefits associated with better territories. Some divorces appeared to be forced evictions by older females, although direct evidence for this is limited. Taken together, our findings demonstrate the complexity of factors that affect the occurrence of divorce when partner choice is constrained.

Early‐life telomere length predicts lifespan and lifetime reproductive success in a wild bird

“…Social groups, consisting of a dominant breeding pair and 0–8 subordinates, defend year‐round stable territories which are distributed linearly along water courses (Kingma, Hall, & Peters, ). Breeding pairs, identified by duet song (Hall & Peters, ), are monogamous (with <5% extra‐pair paternity [Kingma, Hall, & Peters, ]) and can breed all year round with a peak in breeding activity during the wet season (December–March; Hidalgo Aranzamendi et al, ). Subordinates, often retained previous offspring, do not gain parentage until they acquire an independent breeding position, on average around 1.5 years of age.…”

Rapid plastic breeding response to rain matches peak prey abundance in a tropical savanna bird

“…In all models, month (1 = July) was included as a cyclic variable (1 or 12 had the same weight) to control for climate‐independent seasonal variation in nest success (Hidalgo Aranzamendi, ; Zuur et al, ). Habitat quality and group size were added to all models as fixed effects (as in Hidalgo Aranzamendi, Hall, Kingma, Sunnucks, & Peters, ).…”

From ornament to armament or loss of function? Breeding plumage acquisition in a genetically monogamous bird

“…From July 2005 to March 2011, weekly population censuses were conducted year‐round (01 July = start of austral year) to document group size and social status of each uniquely colour‐banded male. From October 2011 to November 2016, this information was recorded biannually in population censuses in October‐November and May‐June (for details see Hidalgo Aranzamendi et al., ; Fan et al., ). At each sighting, each observer scored the extent of breeding plumage on a scale between 0% and 100% in 5% increments; finer scores could be assigned when birds were captured.…”

“…At each sighting, each observer scored the extent of breeding plumage on a scale between 0% and 100% in 5% increments; finer scores could be assigned when birds were captured. Parentage of local birds was determined using six or nine microsatellite loci (for details see Kingma et al., ; Hidalgo Aranzamendi et al., ). In addition, throughout the study, birds were routinely captured to measure tarsus length (a measure of body size).…”

“…The timing of moult into breeding plumage by male fairy‐wrens is viewed as a classic female choice‐driven trait: early moult is strongly selected by female choice for extra‐pair (EP) mates who dominate fertilisations (Peters et al., ; Brouwer et al., ; Figure ). However, EP mating is very limited in M. coronatus (<5% of broods) and mostly driven by incest avoidance (Hidalgo Aranzamendi, Hall, Kingma, Sunnucks & Peters, ; Kingma, Hall & Peters, ; Kingma, Hall, Segelbacher & Peters, ), suggesting no role of female EP mate choice in the evolution of male breeding plumage in this species (Figure ). In addition, there is no apparent reproductive benefit of early moult (Fan et al., ) which, based on the most recent phylogeny (Marki et al., ), may thus constitute a vestigial sexual trait (Figure ).…”