| 1. |
- Barnaby, Jonathan, 1965-, et al.
(författare)
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The role of nepotism, cooperation, and competition in the avian families
- 2010
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Bok (refereegranskat)abstract
- A large number of bird species live in stable groups, and this sets the scene for complex social behaviours, such as cooperative breeding. The vast majority of groups consist of families which arise when young postpone dispersal and remain with their parents beyond independence. However, the factors selecting for the evolution of families and thus also cooperative breeding among birds, are still a challenging puzzle. The currently accepted key explanation for the evolution of families and cooperative breeding focuses on dispersal constraints. While constraints successfully explain within‐population dispersal decisions, they fail as an ultimate explanation because offspring in the majority of species face some sort of dispersal constraint, yet still disperse promptly. Recent alternative explanations focus on the role of philopatry and nepotism, and emphasise a key role of life‐history for the evolution of families. Phylogenetic analyses and field studies have indicated that living in family groups is far more widespread among long‐lived species than short‐lived ones. A long lifespan gives parents the opportunity to invest in their offspring for a prolonged period, while this option is less viable for short‐lived species. Thus, living with nepotistic parents provides offspring with direct fitness benefits that can select for the evolution of family living beyond independence. Nevertheless this generalisation is brought into question since many long‐lived bird species do not live in family groups. An alternative approach attempts to explain family living through the variation in territory quality. Here the incentive to remain with the parents is created by the availability of resources on the natal territory independent of parental nepotism. However, there is not only cooperation, conflicts are also common place in families. Living with independent, sexually mature offspring can lead to conflicts through a change in resource availability or the death of aparent. Therefore families can be expected to be dynamic societies where both parent and offspring decisions depend on each other, and family maintenance depends upon the current ecological conditions. Based on this background, here we review recent studies that have investigated the processes that facilitate family formation, and which highlight both cooperation and conflict that arises from living in family groups. We examine the strengths of current models and explore ideas for a more coherent framework in which to understand prolonged family association in birds. We argue that two paths lead to family living, depending on the life-history. In medium-short lived species where the postponement of independent reproduction comes at a high cost, offspring can benefit from an association with their parents until the next breeding season. In longer-lived species, offspring actually benefit from postponing the onset of independent reproduction, making family living beyond the first year of life an adaptive strategy, and giving the option for cooperative breeding. These processes are illustrated by 5 species-specific case studies. We then finally suggest a number of key questions to developing a deeper understanding of the evolution of family living in birds.
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| 2. |
- Griesser, Michael, et al.
(författare)
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Causes of Ring-Related Leg Injuries in Birds – Evidence and Recommendations from Four Field Studies
- 2012
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- One of the main techniques for recognizing individuals in avian field research is marking birds with plastic and metal leg rings. However, in some species individuals may react negatively to rings, causing leg injuries and, in extreme cases, the loss of a foot or limb. Here, we report problems that arise from ringing and illustrate solutions based on field data from Brown Thornbills (Acanthiza pusilla) (2 populations), Siberian Jays (Perisoreus infaustus) and Purple-crowned Fairy-wrens (Malurus coronatus). We encountered three problems caused by plastic rings: inflammations triggered by material accumulating under the ring (Purple-crowned Fairy-wrens), contact inflammations as a consequence of plastic rings touching the foot or tibio-tarsal joint (Brown Thornbills), and toes or the foot getting trapped in partly unwrapped flat-band colour rings (Siberian Jays). Metal rings caused two problems: the edges of aluminium rings bent inwards if mounted on top of each other (Brown Thornbills), and too small a ring size led to inflammation (Purple-crowned Fairy-wrens). We overcame these problems by changing the ringing technique (using different ring types or larger rings), or using different adhesive. Additionally, we developed and tested a novel, simple technique of gluing plastic rings onto metal rings in Brown Thornbills. A review of studies reporting ring injuries (N = 23) showed that small birds (<55 g body weight) are more prone to leg infections while larger birds (>35 g) tend to get rings stuck over their feet. We give methodological advice on how these problems can be avoided, and suggest a ringing hazard index to compare the impact of ringing in terms of injury on different bird species. Finally, to facilitate improvements in ringing techniques, we encourage online deposition of information regarding ringing injuries of birds at a website hosted by the European Union for Bird Ringing (EURING).
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| 3. |
- Griesser, Michael
(författare)
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Dark or Short Nights: Differential Latitudinal Constraints in Nestling Provisioning Patterns of a Nocturnally Hunting Bird Species
- 2012
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- In diurnal bird species, individuals breeding at high latitudes have larger broods than at lower latitudes, which has been linked to differences in the daily time available for foraging. However, it remains unclear how latitude is linked with parental investment in nocturnal species. Here, we investigate nestling provisioning rates of male Tengmalm's owls in two populations at different latitudes (Czech Republic 50 degrees N; Finland 63 degrees N) with the help of cameras integrated into nest boxes. Clutch sizes were smaller in the Czech population (CZ: 5.1+/-0.1; FIN: 6.6+/-0.1), but given the higher nestling mortality in the Finnish population, the number of fledglings did not differ between the two populations (CZ: 3.5+/-0.3; FIN: 3.9+/-0.2). Nestling provisioning patterns varied within days, over the reproductive season and between the two sites. Males delivered most food at dusk and dawn, having peak delivery rates at sun angles of -11 degrees to -15 degrees at both sites, and males increased the prey delivery rates with higher nestling requirements. Given the longer nights during summer in the Czech Republic compared to Finland, Czech males only showed a small shift in their delivery peak during the night from -17 degrees in April to -14 degrees in July. In contrast, Finnish males shifted their peak of prey delivery from -11 degrees in April to -1 degrees in July. Consequently, Czech males had a longer hunting time per night around midsummer when feeding young (360 min) than Finnish males (270 min). This suggests that nocturnal owl species in northern populations are constrained by the short nights during the breeding season, which can limit the number of young they can raise. Moreover, owls in northern populations are additionally constrained through the unpredictable changes in food availability between years, and both these factors are likely to influence the reproductive investment between populations.
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| 4. |
- Griesser, Michael, et al.
(författare)
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Long-term effects of forest management on territory occupancy and breeding success of an open-nesting boreal bird species, the Siberian jay
- 2012
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 271, s. 58-64
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Tidskriftsartikel (refereegranskat)abstract
- In large parts of the world forests are intensively managed, affecting stand structure and biodiversity. Since re-growth of trees can be slow and management cycles can span over 100 years, long-term longitudinal data are needed to assess the effects of forestry on organisms living in these habitats. Here, we draw upon 50 years of population data of an open-nesting, sedentary bird species, typically of boreal forests, the Siberian jay (Perisoreus infaustus). Forests at the study site were managed by clear-cutting and re-plantation, and a management cycle spanning over 120 years. We tracked changes in forest structure in the nest vicinity and the whole territory with the help of aerial images, and linked them to territory occupancy and offspring production in 13 territories. While territories were occupied in 77.2% of all instances, reproduction was only successful in 19.6% of all instances. Both parameters were positively influenced by a large proportion of unthinned forests older than 50 years, which provide visual protection from nest and adult predators. Thus, it is crucial to assess both territory occupancy and reproductive output to understand the effects of forestry on bird populations. Moreover, our results suggest that in forests with slow turnover cycles, management which avoids thinning (such as green tree retention forestry) can promote population persistence of open-nesting bird species.
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| 5. |
- Griesser, Michael, et al.
(författare)
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Understanding Animal Group-Size Distributions
- 2011
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- One of the most striking aspects of animal groups is their remarkable variation in size, both within and between species. While a number of mechanistic models have been proposed to explain this variation, there are few comprehensive datasets against which these models have been tested. In particular, we only vaguely understand how environmental factors and behavioral activities affect group-size distributions. Here we use observations of House sparrows (Passer domesticus) to investigate the factors determining group-size distribution. Over a wide range of conditions, we observed that animal group sizes followed a single parameter distribution known as the logarithmic distribution. This single parameter is the mean group size experienced by a randomly chosen individual (including the individual itself). For sparrows, the experienced mean group size, and hence the distribution, was affected by four factors: morning temperature, place, behavior and the degree of food spillage. Our results further indicate that the sparrows regulate the mean group size they experience, either by groups splitting more or merging less when local densities are high. We suggest that the mean experienced group size provides a simple but general tool for assessing the ecology and evolution of grouping.
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| 6. |
- Griesser, Michael, et al.
(författare)
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What are the strengths and limitations of direct and indirect assessment of dispersal? : Insights from a long-term field study in a group-living bird species
- 2014
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Ingår i: Behavioral Ecology and Sociobiology. - : Springer Science and Business Media LLC. - 0340-5443 .- 1432-0762. ; 68:3, s. 485-497
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Tidskriftsartikel (refereegranskat)abstract
- Molecular methods of assessing dispersal have become increasingly powerful and have superseded direct methods of studying dispersal. Although now less popular, direct methods of studying dispersal remain important tools for understanding the evolution of dispersal. Here, we use data from Siberian jays Perisoreus infaustus, a group-living bird species, to compare natal dispersal distances and rates using visual mark-recapture, radio-tracking and microsatellite data. Siberian jays have bimodal natal dispersal timing; socially dominant offspring remain with their parents for up to 5 years (delayed dispersers), while they force their subordinate brood mates to leave the parental territory at independence (early dispersers). Early dispersers moved about 9,000 m (visual mark-recapture, radio-tracking) before settling in a group as a non-breeder. In contrast, delayed dispersers moved about 1,250 m (visual mark-recapture only) and mainly moved to a breeding opening. Dispersal distances were greater in managed habitat compared to natural habitat for both early and delayed dispersers. Molecular estimates based on 23 microsatellite loci and geographical locations supported distance estimates from the direct methods. Our study shows that molecular methods are at least 22 times cheaper than direct methods and match estimates of dispersal distance from direct methods. However, molecular estimates do not give insight into the behavioural mechanisms behind dispersal decisions. Thus, to understand the evolution of dispersal, it is important to combine direct and indirect methods, which will give insights into the behavioural processes affecting dispersal decisions, allowing proximate dispersal decisions to be linked to the ultimate consequences thereof.
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| 7. |
- Liu, Yang, et al.
(författare)
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Environmental factors influence both abundance and genetic diversity in a widespread bird species
- 2013
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 3:14, s. 4683-4695
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Tidskriftsartikel (refereegranskat)abstract
- Genetic diversity is one of the key evolutionary variables that correlate with population size, being of critical importance for population viability and the persistence of species. Genetic diversity can also have important ecological consequences within populations, and in turn, ecological factors may drive patterns of genetic diversity. However, the relationship between the genetic diversity of a population and how this interacts with ecological processes has so far only been investigated in a few studies. Here, we investigate the link between ecological factors, local population size, and allelic diversity, using a field study of a common bird species, the house sparrow (Passer domesticus). We studied sparrows outside the breeding season in a confined small valley dominated by dispersed farms and small-scale agriculture in southern France. Population surveys at 36 locations revealed that sparrows were more abundant in locations with high food availability. We then captured and genotyped 891 house sparrows at 10 microsatellite loci from a subset of these locations (N=12). Population genetic analyses revealed weak genetic structure, where each locality represented a distinct substructure within the study area. We found that food availability was the main factor among others tested to influence the genetic structure between locations. These results suggest that ecological factors can have strong impacts on both population size per se and intrapopulation genetic variation even at a small scale. On a more general level, our data indicate that a patchy environment and low dispersal rate can result in fine-scale patterns of genetic diversity. Given the importance of genetic diversity for population viability, combining ecological and genetic data can help to identify factors limiting population size and determine the conservation potential of populations.
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| 8. |
- Nystrand, Magdalena, et al.
(författare)
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Habitat-specific demography and source-sink dynamics in a population of Siberian jays
- 2010
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 79:1, s. 266-274
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Tidskriftsartikel (refereegranskat)abstract
- There are a number of models describing population structure, many of which have the capacity to incorporate spatial habitat effects. One such model is the source-sink model, that describes a system where some habitats have a natality that is higher than mortality (source) and others have a mortality that exceeds natality (sink). A source can be maintained in the absence of migration, whereas a sink will go extinct. 2. However, the interaction between population dynamics and habitat quality is complex, and concerns have been raised about the validity of published empirical studies addressing source-sink dynamics. In particular, some of these studies fail to provide data on survival, a significant component in disentangling a sink from a low quality source. Moreover, failing to account for a density-dependent increase in mortality, or decrease in fecundity, can result in a territory being falsely assigned as a sink, when in fact, this density-dependent suppression only decreases the population size to a lower level, hence indicating a 'pseudo-sink'. 3. In this study, we investigate a long-term data set for key components of territory-specific demography (mortality and reproduction) and their relationship to habitat characteristics in the territorial, group-living Siberian jay (Perisoreus infaustus). We also assess territory-specific population growth rates (r), to test whether spatial population dynamics are consistent with the ideas of source-sink dynamics. 4. Although average mortality did not differ between sexes, habitat-specific mortality did. Female mortality was higher in older forests, a pattern not observed in males. Male mortality only increased with an increasing amount of open areas. Moreover, reproductive success was higher further away from human settlement, indicating a strong effect of human-associated nest predators. 5. Averaged over all years, 76% of the territories were sources. These territories generally consisted of less open areas, and were located further away from human settlement. 6. The source-sink model provides a tool for modelling demography in distinct habitat patches of different quality, which can aid in identifying key habitats within the landscape, and thus, reduce the risk of implementing unsound management decisions.
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| 9. |
- Schneider, Nicole, et al.
(författare)
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Incubating females use dynamic risk assessment to evaluate the risk posed by different predators
- 2013
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 24, s. 47-52
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Tidskriftsartikel (refereegranskat)abstract
- Uncertainty poses a substantial problem for animals, making it is essential for individuals to anticipate changes in their environment to select suitable behavioral strategies. In nest-building species where parents care for dependent young, predation is a major cause of reproductive failure. However, because parents generally have inadequate information about nest predation risks, attaining information about predation hazards increases their likelihood of making informed, optimal decisions. Risk assessment should therefore be widespread, particularly in incubating parents of species that breed in cavities or closed nests, which have limited information about predator presence. This study experimentally investigated the dynamic risk assessment in incubating female brown thornbill (Acanthiza pusilla), a long-lived Australian passerine, which builds closed dome nests in dense vegetation. When the females were exposed to the calls of a nest predator, a predator of adults, and a nonpredatory species, they reacted most strongly to the predator of adults' calls, by looking out of the nest for longest. Females significantly increased their level of alertness on hearing calls of both predator species and maintained their higher level of alertness after the simulated predator presence ended. Females in nests with a high degree of visual cover, and therefore a larger information deficit, reacted more strongly to predator calls than females in more open nests. Moreover, poorly concealed nests had a higher probability of being predated. These results show that incubating female thornbills use dynamic risk assessment and base their response on who is at risk and the degree of information deficit.
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