The effect of climate change on avian offspring production: A global meta-analysis

Climate change affects timing of reproduction in many bird species, but few studies have investigated its influence on annual reproductive output. Here, we assess changes in the annual production of young by female breeders in 201 populations of 104 bird species (N = 745,962 clutches) covering all continents between 1970 and 2019. Overall, average offspring production has declined in recent decades, but considerable differences were found among species and populations. A total of 56.7% of populations showed a declining trend in offspring production (significant in 17.4%), whereas 43.3% exhibited an increase (significant in 10.4%). The results show that climatic changes affect offspring production through compounded effects on ecological and life history traits of species. Migratory and larger-bodied species experienced reduced offspring production with increasing temperatures during the chick-rearing period, whereas smaller-bodied, sedentary species tended to produce more offspring. Likewise, multi-brooded species showed increased breeding success with increasing temperatures, whereas rising temperatures were unrelated to reproductive success in single-brooded species. Our study suggests that rapid declines in size of bird populations reported by many studies from different parts of the world are driven only to a small degree by changes in the production of young.This meta-analysis was financed by the grant of the Polish National Science Centre (Narodowe Centrum Nauki) (no. 2017/27/B/NZ8/00465) awarded to Lucyna Hałupka.Peer reviewe

The effect of climate change on avian offspring production: A global meta-analysis

Climate change affects timing of reproduction in many bird species, but few studies have investigated its influence on annual reproductive output. Here, we assess changes in the annual production of young by female breeders in 201 populations of 104 bird species (N = 745,962 clutches) covering all continents between 1970 and 2019. Overall, average offspring production has declined in recent decades, but considerable differences were found among species and populations. A total of 56.7% of populations showed a declining trend in offspring production (significant in 17.4%), whereas 43.3% exhibited an increase (significant in 10.4%). The results show that climatic changes affect offspring production through compounded effects on ecological and life history traits of species. Migratory and larger-bodied species experienced reduced offspring production with increasing temperatures during the chick-rearing period, whereas smaller-bodied, sedentary species tended to produce more offspring. Likewise, multi-brooded species showed increased breeding success with increasing temperatures, whereas rising temperatures were unrelated to repro- ductive success in single-brooded species. Our study suggests that rapid declines in size of bird populations reported by many studies from different parts of the world are driven only to a small degree by changes in the production of young

Nest boxes for Cape Parrots Poicephalus robustus in the Hogsback area, Eastern Cape, South Africa

Breeding propensity of tree-cavity nesting bird species are often limited by a shortage of natural nesting sites. Artificial nests can be used to provide alternative nest sites. Cape Parrots Poicephalus robustus are nationally endangered and nest in existing tree-cavities in high-altitude fragmented Afromontane forests in South Africa, assumed to be in short supply due to historic and current logging practices. To increase nest site availability, 179 wooden bird boxes and 28 bee boxes (to ‘pull’ bees) were erected during 2011–2012 in Hogsback, Eastern Cape. In 2016, no bird boxes were occupied by Cape Parrots. A total of 43% were used by other species, 51% were unused and 6% could not be inspected due to tree instability and inaccessibility. Two bird boxes were inspected by two pairs of Cape Parrots, but were never occupied. Occupancy of boxes by birds was not associated with nest, tree or habitat characteristics. However, occupancy of boxes by bees was associated with habitat type and tree species. Future conservation efforts will include locating natural Cape Parrot nesting sites and reforestation efforts to ensure the long-term availability of natural nesting sites

Nest boxes for Cape Parrots <i>Poicephalus robustus</i> in the Hogsback area, Eastern Cape, South Africa

<p>Breeding propensity of tree-cavity nesting bird species are often limited by a shortage of natural nesting sites. Artificial nests can be used to provide alternative nest sites. Cape Parrots <i>Poicephalus robustus</i> are nationally endangered and nest in existing tree-cavities in high-altitude fragmented Afromontane forests in South Africa, assumed to be in short supply due to historic and current logging practices. To increase nest site availability, 179 wooden bird boxes and 28 bee boxes (to ‘pull’ bees) were erected during 2011–2012 in Hogsback, Eastern Cape. In 2016, no bird boxes were occupied by Cape Parrots. A total of 43% were used by other species, 51% were unused and 6% could not be inspected due to tree instability and inaccessibility. Two bird boxes were inspected by two pairs of Cape Parrots, but were never occupied. Occupancy of boxes by birds was not associated with nest, tree or habitat characteristics. However, occupancy of boxes by bees was associated with habitat type and tree species. Future conservation efforts will include locating natural Cape Parrot nesting sites and reforestation efforts to ensure the long-term availability of natural nesting sites.</p

Monitoring an isolated population of Cape Parrots Poicephalus robustus in the Limpopo province, South Africa

Cape Parrots Poicephalus robustus inhabit forest patches in South Africa with &lt;1 800 individuals remain in the wild. A small, genetically isolated population occurs in the northern part of its range in the Limpopo province. There, annual counts indicated ~100 remain, but count numbers fluctuate substantially between years creating uncertainty over population trends. To inform approaches to the monitoring of Cape Parrot populations in the Limpopo province, we investigated how local abundance counts varied within and across years at known parrot ‘hotspots’. Monthly counts were done at these sites during 2013–2015 and 2020–2021. We found large variability in counts both within and amongst years, although this differed between sites. Observations of behaviour suggest that a site close to overnight roosts was more reliable, whereas those close to food sources were more variable likely linked to fruit availability. The highest numbers were recorded at a pecan nut orchard away from the indigenous forest. To better understand population trends of this small, isolated population we recommend annual counts are complemented with a series of focused counts at pecan nut orchards, which are monitored with greater intensity during the fruiting season. Keywords: census; conservation; nomadic; parrot; population estimat

Natal dispersal in the Southern Ground Hornbill Bucorvus leadbeateri

Dispersal is of ecological and evolutionary importance for population biology because it affects a species’ ability to expand its range, to colonise new favourable habitats and to increase the likelihood of population persistence. Male birds are mostly philopatric, delaying dispersal or dispersing closer to their natal territories than females. Females tend to disperse further than their male siblings to reduce the chance of inbreeding. Dispersal in the cooperative breeding Southern Ground Hornbill Bucorvus leadbeateri is poorly understood. It is not known how far individuals disperse, or what the difference in dispersal age and distance is between males and females. We investigated dispersal events using field observations of ringed individuals within groups in a study population and resightings in surrounding areas. A total of 113 individuals from 19 groups were ringed during 2005–2015. Of these, 14 were breeding adults who never dispersed. Of the remaining 99, 27 were still present in their natal groups at the end of the study, four deaths were confirmed, 50 disappeared from their group and were never seen again (excluded from further analysis), and 18 were confirmed to have dispersed by direct observations in secondary groups. Median dispersal distance was similar for females and males (22 km and 25 km, respectively). Females dispersed younger than males (eight months post-fledging and 44 months post-fledging, respectively). One male delayed dispersal beyond nine years and all females dispersed before three years post-fledging. These data provide insights into the dispersal dynamics and dispersal propensity of this endangered species. Ways to improve data collection and the study of dispersal in this species are discussed.Keywords: cooperative breeding, dispersal, ground hornbills, philopatry, resighting

The effect of climate change on avian offspring production: A global meta-analysis

Climate change affects timing of reproduction in many bird species, but few stud-ies have investigated its influence on annual reproductive output. Here, we assess changes in the annual production of young by female breeders in 201 populations of 104 bird species (N = 745,962 clutches) covering all continents between 1970 and 2019. Overall, average offspring production has declined in recent decades, but considerable differences were found among species and populations. A total of 56.7% of populations showed a declining trend in offspring production (significant in 17.4%), whereas 43.3% exhibited an increase (significant in 10.4%). The results show that climatic changes affect offspring production through compounded effects on ecological and life history traits of species. Migratory and larger-bodied species experienced reduced offspring production with increasing temperatures during the chick-rearing period, whereas smaller-bodied, sedentary species tended to produce more offspring. Likewise, multi-brooded species showed increased breeding success with increasing temperatures, whereas rising temperatures were unrelated to repro-ductive success in single-brooded species. Our study suggests that rapid declines in size of bird populations reported by many studies from different parts of the world are driven only to a small degree by changes in the production of young