Habitat use,nest-sites and chick diet of Grey Partridge Perdix perdix on hill farms in north east England

Capsule: Breeding Grey Partridges Perdix perdix on hill farms preferred Soft Rush-infested rough grazing which provided nesting cover and invertebrates for foraging chicks.

Aims: To measure habitat use, nest sites, chick diet and breeding productivity of Grey Partridge on hill farms in north east England.

Methods: We measured actual habitat use of radio-tagged individuals in relation to its availability both within home ranges and over the wider study area. Nesting habitat and breeding productivity data were collected from radio-tagged pairs. Faecal samples from roost sites of broods were collected to assess chick diet.

Results: Grey Partridges preferred rough grazing habitats. Sixty-nine per cent of nests were found in rough grazing with females preferring to nest in tall rushes which provided cover. Chick diet differed between habitats and in relation to brood age. In rough grazing, sawfly larvae were the most numerous item eaten by young (46%) and older broods (27%).

Conclusion: On hill farms, breeding Grey Partridges preferred rough grazings, where broods preferred sawfly larvae. It is important that rush-infested rough grazings are not agriculturally improved and grazing regimes that provide abundant sawfly larvae are practised.     

Artificial nests for Barn Swallows Hirundo rustica: a conservation option for a declining passerine?

Capsule: Barn swallows Hirundo rustica using artificial nest cups had greater reproductive success than those building and using natural nests.

Aims: To quantify reproductive success of Barn Swallows breeding in artificial man-made nests and compare with those using natural nests.

Methods: In 2012–16, the breeding attempts of 231 pairs of Barn Swallows were monitored in artificial and natural nests in an urban habitat in Denmark.

Results: Pairs breeding in old natural nests and artificial nests bred earlier, laid more eggs, and produced more nestlings and fledglings than pairs breeding in new natural nests. Inter-clutch intervals were shorter in Barn Swallow pairs using artificial nests and old natural nests. Nest cup volume and nest volume of newly built nests were significantly larger and more variable than artificial nests excluding an effect of nest size as an explanation for the larger clutches laid in artificial nests. Increased energy and time costs of nest construction may have reduced reproductive success for pairs building natural nests.

Conclusion: Artificial nests were readily accepted by Barn Swallows, they had a similar low predation rate as natural nests, and they proved to be a possible conservation option for this declining passerine breeding in urban habitats as evidenced by their 75% higher reproductive success in artificial nests.     

Playback survey trial for the Little Owl Athene noctua in the UK

Capsule: Playback is effective at improving detectability of Little Owls.

Aims: To trial a playback survey methodology for Little Owls in the UK to determine detectability and practicalities which could inform potential future national monitoring efforts.

Methods: Nocturnal playback surveys were carried out in an open landscape in the east of England in spring 2015. Twelve 2?×?2?km survey squares were each visited four times. Little Owl calls were broadcast from three locations within each square along a linear transect and spaced 500 m apart. The responses of owls of any species were recorded. Little Owl occupancy was later confirmed through existing nest monitoring efforts.

Results: Little Owls were detected responding to playback in all survey squares and were confirmed to be breeding in 8 of the 12. Detection and response rates were greater when combining data from multiple broadcast locations. The likelihood of Little Owls responding decreased with greater distance of broadcast location to known nest site, but no relationships were identified with time of evening or the presence of other owl species.

Conclusion: Playback methodology proved to be effective at increasing detectability of Little Owls and this study provides an estimated response rate to inform future efforts.     

Habitat characteristics of breeding Eurasian Whimbrel Numenius phaeopus on Mainland Shetland,Scotland, UK

Capsule: Habitats used by Whimbrel Numenius phaeopus chicks for feeding are significantly different to those used by adults for feeding and nesting.

Aim: To identify habitats used by breeding Whimbrel on Mainland Shetland.

Methods: Fourteen study sites were used to identify three main components of Whimbrel breeding habitats: (i) adult territorial and foraging habitats; (ii) nest site habitats; (iii) chick feeding habitats. The relationship between these components was investigated using principal components analysis.

Results: Habitats used by adults comprised blanket bog dominated by ling heather, cross-leaved heath, common cottongrass, hare’s-tail cottongrass, deergrass and purple moor-grass. There was a thick layer of bryophytes but few forbs. Habitat used for nesting was similar to the general habitat used by adults. The habitats in which Whimbrel chicks foraged were significantly different in structure from the habitats used by adults. The chick feeding areas were characterized by small, wet and often linear features.

Conclusion: Habitat requirements by Whimbrel chicks for foraging differed from those of adult Whimbrel for nesting. Habitat structure is important for chicks and the presence of small, wet linear features may be a limiting component on otherwise apparently suitable adult Whimbrel habitats.     

Nest timing,nest site selection and nest structure in a high latitude population of Bearded Reedlings Panurus biarmicus

Capsule: Bearded Reedlings Panurus biarmicus show consistent nest timing, select old, compacted areas of reed when positioning their nests, and may adjust nest structure in relation to local reed characteristics and temperature.

Aims: To investigate the nest timing, nest site selection and nest structure of a rare and elusive passerine, the Bearded Reedling at the northern limit of this species’ range.

Methods: A sample of Bearded Reedling nests from the Tay Reedbeds in Scotland were located and monitored with regard to the timing of nesting, fate, fine-scale habitat characteristics and nest structure.

Results: First egg dates and brood sizes were consistent between years of the study despite variation in spring temperatures. Bearded Reedlings nested within unmanaged patches of reed, positively selecting deep leaf litters and compacted reed. Attributes of nest structure, namely internal and external diameter, were influenced by nest site characteristics and local temperature.

Conclusion: Despite a limited sample size, the study suggests that reedbed management should ensure adequate areas of old, dry and unmanaged reed are available when aiming to encourage breeding Bearded Reedlings. Additionally, the apparently flexible structure of the nest may assist this species when coping with changeable climatic conditions.     

Productivity of the Black-legged Kittiwake Rissa tridactyla required to maintain numbers

Capsule: To maintain the breeding numbers in Britain, Black-legged Kittiwakes Rissa tridactyla need to produce a mean of 0.8–1.5 fledged young per year.

Aims: To obtain a new estimate for the number of young Kittiwakes fledged per pair required to maintain breeding numbers in Britain in the period 1985–2015 based on field data.

Methods: The annual values of productivity in the River Tyne area of northeast England are compared with the long-term increases in numbers of breeding pairs in that area. Regressions between the annual productivity and the corresponding change in breeding numbers at 12 sites in Britain are used for the periods 1985–2000 and 15 sites for 2000–15.

Results: A long series of records of the annual productivity of Kittiwakes, where breeding pairs increased progressively over 61 years, showed that an annual productivity of 1.5 young fledged per pair was an extremely rare event. Over the periods 1985–2000 and 2000–15 regressions of the change in breeding numbers against mean annual productivity for 15 sites indicated that about 0.8 fledglings per pair were needed to maintain breeding numbers and this value remained unchanged over the 30 years, suggesting that adult mortality rates had not changed over this period of time.

Conclusion: The decline of Kittiwakes in Britain has occurred because fewer than 0.8 chicks per pair have been fledged at many sites in recent years. The mortality rate of adult Kittiwakes breeding in Britain 1985–2015 does not indicate an increase over time and so is unlikely to have been a major contributor to the decline in breeding numbers.     

Variation in nest composition and abundances of ectoparasites between nests in colonially breeding Common Eiders Somateria mollissima

Capsule: The occurrence of high numbers of ectoparasites in nests of Common Eiders may be related to nest densities and nesting behaviour.

Aims: To estimate abundances of ectoparasites and occurrence of blood-covered eggs, and relate those to nest bowl ages, nest bottom material and the incubation stages of eggs, in nests at two different Common Eider colonies.

Methods: Nests were collected at Hvallátur and Rif, two sites at Breiðafjörður, West Iceland, in June and July 2012. The nest bottom material was classified to vegetation species and invertebrates were identified to species when possible.

Results: The flea Ceratophyllus garei was the dominant ectoparasite at both sites, with median abundances higher at Hvallátur than at Rif in June. In July, the mean abundance of fleas was higher than observed in June at Rif. There were positive relationships between the flea abundances and the incubation stages of the nests, the blood cover of the eggs and the type of nesting material. No relationship was observed between the age of nesting bowls and adult flea abundances.

Conclusion: Disadvantages of large parasite loads on the later nesters (second clutch in each nest) at Rif may be compensated by shared nest attendance and the concurrent added time for preening for females while other females attend their nests.     

The ecology of Black Guillemot Cepphus grylle grylle chicks in the Baltic Sea region: insights into their diet,survival, nest predation and moment of fledging

Capsule: The diet of Black Guillemot Cepphus grylle grylle chicks in the Baltic Sea region was dominated by Viviparous Eelpout Zoarces viviparus. Risk of nest predation by avian and mammalian predators was perceived to be low, and hatching and fledging success were high.

Aims: To gain insight into the ecology of nestling Black Guillemots in the Baltic Sea region to fill knowledge gaps and benefit its conservation.

Methods: Two island groups in the Baltic Sea were visited several times during the breeding season of 2014 and 2015 to monitor nestling survival and fledging. In addition, camera traps were used in 2014 to monitor prey brought to chicks by adults and record possible nest predation events.

Results: Hatching success was 0.89 and 0.73 in 2014 and 2015, respectively, and fledging success was very high (0.95 and 0.97). No incidences of avian or mammalian predation were observed. Chicks fledged at night between 32 and 38 days after hatching. Viviparous Eelpout made up 95% of the prey items brought to the chicks by adults.

Conclusions: The hatching rate and fledging rate of the Black Guillemot was high in our study region. Juveniles seemed highly dependent on the availability of eelpout. Changes in the abundance of this species may therefore have negative effects on chick survival.     

Nest survival,causes of failure and productivity of British Hawfinches Coccothraustes coccothraustes

Capsule: Nest success rate of Hawfinches Coccothraustes coccothraustes within our study areas averaged 36% across five seasons, a level unlikely to be driving population declines and considerably higher than was suggested by recent estimates from the long-term Nest Record Scheme.

Aims: To investigate potential habitat correlates of nest success and identify nest predators from an intensive study on Hawfinches. To compare nest success and habitat of these nests with those found by Nest Record Scheme (NRS) recorders and test whether there is evidence of a decline in nest success over time from the NRS data.

Methods: Females trapped at feed sites were fitted with radio-tags and tracked back to nest sites providing a sample of nests for subsequent monitoring. Habitat measures potentially influencing survival were collected at nest sites and modelled against nest outcome. Nest success was compared with that from the long-term Nest Record Scheme. Nest cameras were deployed to identify predators.

Results: Nest success varied among years, but the mean value was not substantially lower than other Hawfinch studies or from other species with similar nesting strategies. Apparent recent declines in success suggested by Nest Record Scheme data were not evident in our study areas. Only avian species were recorded predating nests and a number of partial predations were recorded. No correlation was found between overall success for study nests and the habitat or temporal measurements collected.

Conclusions: Within our study areas, average Hawfinch nest success and productivity appeared to be sufficient to maintain local population stability though our sample size was modest and further work would be beneficial. General nest recording may have inherent biases that lead to an over-estimation of nest failure compared to those found by more structured study. Drivers of recent UK Hawfinch declines may be operating outside of the nesting season and/or in landscapes outside primary woodland.     

Landscape effects on nest site selection and nest success of Northern Lapwing Vanellus vanellus in lowland wet grasslands

Capsule: Northern Lapwing Vanellus vanellus avoid nesting close to small woodland patches but nest predation rates do not vary with distance to woodland patches, either because risky areas are avoided or perceived nest predation risk does not reflect actual risk.

Aims: To explore the effects of woodland patches in wet grassland landscapes on nest distribution and success of Lapwings.

Methods: We quantified the effect of woodland patches on the distribution and outcome of Lapwing nests across four wet grassland sites by mapping nest distribution and monitoring nest outcomes.

Results: Lapwing nested significantly further from woods than expected by chance. Neither nest predation rates nor the probability of predation occurring at night (thus primarily mammalian predators) or day (primarily avian predators) varied in relation to distance from woodland patches.

Conclusions: High levels of nest and chick predation in wet grassland landscapes limit the capacity for breeding wader populations to be self-sustaining. Consequently, identifying manageable landscape features that influence predation rates is an important focus of conservation research. Lapwing avoid breeding close to woodland but, as nest predation rates do not vary with distance from woodland patches, their removal may increase the area of suitable nesting habitat but is unlikely to substantially influence productivity.     

Influence of diet and foraging strategy on reproductive success in two morphologically similar sympatric seabirds

Capsule: Morphologically similar sympatrically breeding species differ in diet and foraging strategies, which could explain interspecific variation in breeding success and reproductive output.

Aims: To compare provisioning rate and diet of nestling Arctic (Sterna paradisaea) and Common Terns (Sterna hirundo), and examine how variation in provisioning behaviour influences reproductive parameters.

Methods: Arctic and Common Tern nests were observed from June to July 2011 on Coquet Island, northeast England. We compared chick provisioning rate, diet and energy delivery rate between species, and examined whether these parameters were associated with interspecific differences in chick growth and survival, and total number of chicks fledged.

Results: Arctic Terns delivered higher percentages of smaller Sandeels (Ammodytes marinus) and juvenile fish to chicks than did Common Terns, which delivered comparatively high percentages of larger Sprats (Sprattus sprattus). Although chick growth rate and survival were not significantly different between species, Common Terns fledged more chicks than Arctic Terns due to a tendency for larger clutch sizes.

Conclusion: Our study suggests that interspecific differences in diet and foraging strategies can support total reproductive output in morphologically similar species.     

Density-dependent regulation of breeding success in the Red-crested Pochard Netta rufina

Capsule: Numbers of breeding Red-crested Pochard Netta rufina in the Czech Republic were positively correlated with reproductive success in the previous year, yet annual productivity, declined with increasing numbers of females at the beginning of the breeding season, suggesting local limiting factors on this population.

Aims: To test the hypothesis that long-term increases in numbers of a breeding population of Red-crested Pochard Netta rufina can be explained by the productivity (numbers of ducklings fledged) in the previous year. We also test for the potential adverse effect of population size on population productivity in the current year.

Methods: Data from 2004 to 2016 from South Bohemia, Czech Republic, were analysed using TRends and Indices for Monitoring Data software to investigate changes in numbers of adults, numbers of females at the start of the breeding season and number of broods produced.

Results: There was a significant increase in the numbers of adults and females at the beginning of each breeding season. Numbers of adults in May positively correlated with productivity (numbers of ducklings fledged) in the previous breeding season, but relative productivity (broods per adult female) in the current year was negatively correlated with females abundance at the beginning of the breeding season.

Conclusions: The study identifies density-dependent regulation as a factor in the population productivity of Red-crested Pochards using intensively managed fishponds as a breeding ground.     

Limited prospecting behaviour of juvenile Eagle Owls Bubo bubo during natal dispersal: implications for conservation

Capsule Features of the breeding population and temporary settlement area influence the behaviour of Eagle Owls Bubo bubo prospecting for breeding sites during natal dispersal.

Aims To understand how prospecting behaviour during natal dispersal is affected by (i) the main characteristics of the breeding and dispersing portions of the population and (ii) main prey availability.

Methods We explored the ten-year dynamics and characteristics of radio-tagged breeders and dispersers of an Eagle Owl population.

Results During the first years following natal dispersal there was little prospecting behaviour of nesting sites and birds remained mainly within non-breeding settlement areas, bordering the sector occupied by the breeding population. Settlement areas had an abundant food supply, and low intraspecific competition and mortality. We suggest that these features of the settlement areas may reduce the willingness of individuals to search for breeding sites and may have the potential to impact on the viability of breeding populations.

Conclusion From a conservation perspective, the lengthy use of the temporary settlement areas by juvenile Eagle Owls suggests that the sites should be considered as important as the breeding areas when planning conservation strategies. Reducing juvenile mortality in settlement areas may represent an overlooked conservation strategy for long-lived species and may have a crucial effect on the viability some animal populations.     

Tawny Owl Strix aluco response to call-broadcasting and implications for survey design

Capsule: The use of call-broadcasting significantly increases the number of Tawny Owls Strix aluco detected in winter point counts, but requires careful survey design to avoid introducing potential sources of bias into population estimates.

Aims: To examine Tawny Owl response to call-broadcasting to aid survey design in national monitoring efforts.

Methods: A nocturnal survey was undertaken at 36 survey points over three nights in winter in Thetford Forest, England. Each survey consisted of four consecutive five-minute segments: a passive count, followed by three counts with the use of call-broadcasting.

Results: Few (4%) Tawny Owls were recorded during passive surveys, whereas the greatest response was during the first and second call-broadcast segments (49% and 36%, respectively). New detections declined to 11% in the final segment. Response was fastest at dusk, although time of night did not significantly affect the number of individuals detected. Male owls accounted for 79% of detections.

Conclusion: Our results show that ten minutes of call-broadcast surveying will detect 85% of responsive Tawny Owls, thus vastly improving detection compared to passive listening alone. However, simultaneous counts of geographically separated detections should be used to provide a minimum count and reduce potential double-counting of mobile individuals.     

Habitat structure modulates nestling diet composition and fitness of Blue Tits Cyanistes caeruleus in the Mediterranean region

Capsule: The nestling diet of Blue Tits Cyanistes caeruleus is influenced by parental effort and habitat type, and consequently has an impact on breeding success.

Aims: In a three-year study, we compared the nestling diet of Blue Tits in two Mediterranean forests (pinewood and oakwood) and tested its implications for breeding success.

Methods: Adults were captured at the nest to obtain morphological measurements, and provisioning behaviour was recorded when chicks were 11 days old. Nestling tarsus length and body mass were measured on day 13 after hatching.

Results: Caterpillars constituted the largest proportion of nestling diet in both habitats, however, higher numbers and biomass of noctuid, as well as higher numbers of tortricid larvae, were provided to nestlings in the pinewood. Furthermore, females provided tortricids more often than males, whereas males supplied more geometrid larvae and spiders. We found a more generalist diet for nestlings raised in the pinewood. Also, a greater number of young fledged when their diet included more tortricids and was more generalist, and Blue Tit nestlings raised on a diet with a higher number of spiders were in better body condition.

Conclusion: Differences in nestling diet between habitat types contribute to explain variance in breeding performance and therefore demonstrate diverse foraging behaviour strategies among populations.     

Hen harrier Circus cyaneus nest sites on the Isle of Mull are associated with habitat mosaics and constrained by topography

Capsule: Hen Harriers Circus cyaneus on the Isle of Mull, UK, are associated with habitat mosaics consisting of moorland, scrub and forestry but avoid grazed land, suggesting that forested habitats could be managed sympathetically for the Hen Harrier in the future should the current UK population increase.

Aims: To use distribution modelling to investigate nesting habitat associations using a long-term data set for the Hen Harrier on Mull.

Methods: We develop area-interaction models using a least absolute shrinkage and selection operator penalty to explore the distribution of 102 Hen Harrier nest sites in relation to habitat and topography. Our model is then successfully validated in tests using data for 70 nest sites from subsequent years.

Results: Our model is effective in predicting suitable areas for Hen Harrier nest sites and indicates that Hen Harriers on Mull are found in habitat mosaics below 200 m above sea level. Hen Harrier nest intensity is positively associated with increasing proportions of moorland and scrub, open canopy forestry and closed canopy forestry. Nest intensity is negatively associated with increasing proportions of grazed land.

Conclusion: Hen Harriers avoid grazed areas but are relatively tolerant of other habitat combinations. These findings are supported by previous observations of Hen Harrier habitat use and have implications for the recovery of some Hen Harrier populations in Special Protection Areas and future forest management. Open canopy forest and forest mosaics could potentially be incorporated into landscape-scale conservation plans for Hen Harriers using the population on Mull as an example.     

Effect of air movement on the thermal insulation of avian nests

Capsule: Air movement over a nest increases the rate of cooling within the nest cup but the walls provide good thermal insulation.

Aims: This study compared nests of six bird species of the families Fringillidae and Motacillidae to investigate the insulative properties in still and moving air treatments. It was hypothesized that differences in nest size and moving air would differ between species and would have a significant effect on insulatory values of the nests.

Methods: Nest dimensions were measured for a total of 35 nests from six species. Thermal properties of the nests were recorded using temperature loggers within nests placed in a wind tunnel under still and moving air conditions.

Results: Insulatory values and internal nest cooling rates were significantly increased by moving air. There was no significant difference between species for the thermal properties of nests but nest mass correlated with greater insulatory values and a lower rate of cooling within the nest cup. Nest wall thickness had no significant effect on the thermal characteristics of the nests.

Conclusion: The use of a constructed nest mitigated the effects of air movement but the differences between species reflected difference in nest mass rather than wall thickness.     

Use of materials in nest construction by Pied Flycatchers Ficedula hypoleuca reflects localized habitat and geographical location

Capsule: Pied Flycatchers Ficedula hypoleuca use different materials to construct their nests according to local availability and geographical location.

Aims: This study tested the hypotheses that Pied Flycatcher nests were constructed from the leaves of different tree species in proportion to their occurrence within the breeding territories and that nest composition varied between geographical locations.

Methods: In Lancashire, Pied Flycatcher nests were collected from nestboxes built in locations dominated by different tree species and were deconstructed to determine which materials were used.

Results: The leaves found in nests generally reflected their availability within the locality of the territories rather than showing evidence of selective use of some leaf species. However, the use of moss was dominated by the use of one species in all but two nests. Nests from Lancashire were significantly different in composition when compared with published data for nests from north Wales and central Spain.

Conclusion: Pied Flycatchers exhibit plasticity in nest construction behaviour because they were opportunistic in their choice of most leaves as nesting materials, although they may be selective in their choice of moss.     

Habitat associations of young Black Grouse Tetrao tetrix broods

Capsule: In the Scottish Highlands, Black Grouse Tetrao tetrix females with young broods selected areas rich in wet flushes, grasses and Sphagnum mosses.

Aims: To identify associations between young Black Grouse broods and habitat characteristics.

Methods: We located brood-rearing Black Grouse females in four areas of moorland-forest mosaic in the Scottish Highlands. Each brood was paired with a random reference location 100?m away. We recorded cover of different habitats and fine-scale vegetation and structure within squares of 1 and 0.25?ha, respectively. Associations between brood occurrence and habitat and vegetation variables were examined at the two scales.

Results: Black Grouse broods were positively associated with wet flushes (1?ha), and with Heather Calluna vulgaris, sedges Carex spp., grasses, Sphagnum mosses and taller vegetation with intermediate levels of height variability (0.25?ha).

Conclusions: This study highlights the importance of wet habitats for young Black Grouse chicks. In addition, relatively tall field-layer vegetation comprising Heather, sedges, grasses over a layer of Sphagnum mosses attracted brood-rearing Black Grouse females. Many management practices associated with peatland restoration, including drain-blocking, Sphagnum re-establishment and the avoidance of burning on deep peat soils, are therefore consistent with favourable habitat management for Black Grouse.