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Life history and ecology of family-living Iberian black wheatears (Collalba negra)



Overview

Cooperative societies are widely distributed in nature and usually arise through prolonged association of parents and offspring. Understanding the evolution of family-living is fundamental to understanding complex social behaviours, such as cooperative breeding in birds and mammals. The two currently accepted key explanations for the evolution of families focus on dispersal constraints, such as a lack of breeding openings due to habitat saturation (i.e., a “best of a bad job” strategy), and the benefits of philopatry, unique benefits found only on the natal territory which positively affect fitness, including nepotism. The latter emphasises a key role of predictable access to resources, particularly through parental maintenance of year-round territories in locations with periods of unfavourable conditions, such as harsh winters in temperate areas. While theory predicts that a combination of ecological constraints and benefits of philopatry select for family cohesion, these theories do not account for the fact that dispersal timing, even within families, can vary considerably. Moreover, much empirical research has explored why some individuals in cooperatively breeding species defer dispersal and forego independent reproduction, yet there has been little investigation into evaluating the causes and consequences of dispersal timing in non-cooperatively breeding species, despite that there is considerable variation both among and within species.


In this project we investigate the factors that explain family-living in our long-term (since 2010) individually-marked study species, the black wheatear. In this species, dispersal timing is bi-modal: most offspring disperse from the natal territory 3-6 weeks after fledgling, but the dominant 1-3 offspring from each pair’s final brood of the season overwinter on the parental territory. This population inhabits a harsh arid environment of hot, dry summers and cold, often snowy, winters, near Guadix, Spain. We combine experiments, observations, and long-term data to test the costs and benefits of the different dispersal strategies of black wheatears and to generally shed light on their life-history and ecology.


Main Research Questions

What benefits are associated with family-living over winter?

For parents to tolerate philopatric offspring in their territory, the benefits of living in a family group must outweigh the costs. It remains unclear what these benefits are for black wheatears. Current research in this population suggests that nepotism plays a minor, if any, role in the retention of juveniles on the natal territory, unlike in other family-living species. Thus, benefits reaped from delayed dispersal in this species may arise through group living benefits rather than family living per se. Such benefits may include effects on foraging efficiency, thermoregulation, and/or defense against predators or intruders. Ongoing research utilizes field experiments and behavioural observations to disentangle these potential advantages of group living in black wheatears.


What are the social and ecological settlement conditions of prompt dispersers?

The black wheatear is listed as “Vulnerable” by the 2015 European Red List (24), and among the reasons listed for needing protection is “Habitat deterioration and severe winters may cause extinctions locally.” Thus, it is important to have a clear picture of the habitat necessary for supporting this species, particularly over winter. Nonetheless, we currently have no information about winter habits or habitat use of those individuals that promptly disperse from their parental territory - the majority of yearling birds. By fitting fledglings with radio transmitters, we can track and observe these birds to elucidate post-dispersal winter conditions.


How does dispersal timing influence first year survival and procurement of a breeding position?

Long-term monitoring of dispersed black wheatears will allow us to evaluate the survival and breeding prospects of the different dispersal strategies.



In addition to the above research questions which are directly related to family living in this species, we also run several projects on communication, sexual selection, and conservation of this species. Contact Gretchen Wagner to discuss project possibilities!



Male wheatear display



feeding wheatear chicks



begging behaviour



Thesis opportunity -
Bimodal dispersal strategies in black wheatears -
radiotracking wild birds (fieldwork in Spain)



Most animals leave their parents when they are independent enough to fend for themselves, but in some species offspring associate with their parents for an extended time. In the black wheatear (Oenanthe leucura) offspring do both; most leave their parents as soon as they can, but a few stick around for many more months. Currently, we have no information about the wintering habitat, social behaviour, or fitness outcomes of the promptly dispersing individuals. By fitting fledglings with radio transmitters, we will be able to track these birds to shed light on their post-dispersal conditions and elucidate the fitness consequences of the divergent strategies. Since increasingly harsh winters are thought to play a critical role in the decline of this species, revealing the winter habits of the majority of first-year birds can inform conservation initiatives.

Projects will run from early spring until late summer in the field site near Guadix, Spain.

Used skills: fieldwork, radiotelemetry, behavioural observation, bird catching, statistics.

Requirements: The fieldwork best suits those that can work well both independently and in a team. Patience and flexibility are essential! A valid driving license and some knowledge of Spanish is beneficial.


Apply here

fieldwork



field location in guadix, spain



bill measurement



associated publications



Wagner GF, Mourocq E, Griesser M. 2019. Distribution of experimentally increased costs of parental care among family members depends on duration of offspring care in biparental birds. Frontiers in Ecology and Evolution 7(366). link

Drobniak SM, Wagner GF, Mourocq EM, Griesser M. 2015. Family living: an overlooked but pivotal social system to understand the evolution of cooperative breeding. Behavioral Ecology 26(3). link

Wagner GF, Mourocq EM, Griesser M. 2019. Elevated nest predation risk promotes offspring size variation in birds with prolonged parental care. EcoEvoRxiv. link



Want to know more ?



You want to do your thesis or internship working on black wheatears,
or you want to know more about this ongoing project ?


Contact Gretchen Wagner



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