House Sparrow Passer Domesticus Populations Research Articles

Invertebrate prey availability limits reproductive success but not breeding population size in suburban House Sparrows Passer domesticus

Factors affecting avian demography and abundance in urban landscapes are poorly understood and this hinders attempts to manage urban bird communities. Several recent studies indicate that lack of invertebrate prey in urban landscapes may constrain avian productivity and fitness relative to that in other habitats. House Sparrow Passer domesticus populations have undergone large declines in many European urban centres and inadequate reproductive success linked to invertebrate availability has been postulated as a potential cause of these declines. We conducted a replicated supplementary feeding experiment to test whether the availability of invertebrate prey limits the breeding success and adult abundance (colony size) of House Sparrows in suburban London, where House Sparrow populations declined by 60% during the decade preceding our study. Daily mealworm provision over two successive breeding seasons, sufficient to provide 82% of chick energy requirements of House Sparrow pairs nesting within 50 m of feeders, had a large positive impact on the abundance of recently fledged birds (+62%), but only a small positive impact, limited mainly to small colonies, on the overall abundance of territorial males. Colony growth was only weakly related to fledgling abundance in the previous year and did not appear to be constrained by nest‐site availability. Conservation interventions that enhance invertebrate availability for suburban House Sparrows may increase reproductive success but are unlikely, on their own, to lead to population growth or recovery.

Using citizen science to investigate the role of productivity in House Sparrow Passer domesticus population trends

Capsule Seasonal variation in garden House Sparrow numbers provides a tool to examine overall annual productivity, measuring the combined success of multiple breeding attempts and post-fledging survival.Aims To develop a metric to use British Trust for Ornithology (BTO) Garden BirdWatch (GBW) data to measure annual productivity in House Sparrows across regions and habitats exhibiting contrasting population trends.Methods We examine variation in annual productivity by quantifying the height of the seasonal peak of garden House Sparrows relative to pre-breeding numbers. We use BTO Nest Record Scheme (NRS) data to explore the demographic drivers of variation in this metric and relate differences to BTO/Joint Nature Conservation Committee/Royal Society for Protection of Birds Breeding Bird Survey regional population trends.Results GBW annual productivity was similar between rural and urban gardens but was lower in the south and the east of Britain (1.32 fledglings per adult), where populations are declining, than in the north and west where populations are stable (1.37 fledglings per adult). Analysis of NRS data showed similar regional variation in clutch and broods sizes.Conclusion The intensity of effort required to measure breeding success directly through nest monitoring has limited the scale of data collection but these results suggest that Garden BirdWatch (GBW) data can provide a measure of annual productivity across multiple sites. Regional variation in annual productivity (primarily driven by reduced clutch sizes) mirrors population trends, suggesting that reduced breeding success may be influencing House Sparrow population recovery.

Changes in the House Sparrow Passer domesticus population in Valencia (Spain) from 1998 to 2008

Capsule The population of House Sparrow Passer domesticus has experienced a sharp decline in the municipality of Valencia. Aims To investigate the population trends of House Sparrows. Methods Between September 1998 and December 2008, House Sparrows were censused monthly in 22 urban parks covering a total of 118 ha. Additionally, birds in the wider urban landscape were censused in 24 plots of about 50 ha during the winter and spring of years 1998, 2003 and 2007. Results The House Sparrow population experienced a significant decline of about 70% over 10 years in urban parks, with monthly peak values decreasing from about 2000 birds in 1998 to about 500 in 2008. Between 1998 and 2007, a significant decline was detected in the urban landscape mostly during the winter. Conclusions Urban parks are a main feeding habitat for House Sparrows, and habitat structure of urban parks has remained similar throughout these years. Therefore, the decreasing number of sparrows recorded in parks probably reflects an overall population decline of the species in Valencia. This decline has coincided with high‐intensity urban development i.e. an increase in the building density and a reduction in the amount of wastelands and other feeding habitats. Thus, shortage of nest‐sites did not seem to be a limiting factor for the population, but a reduction of food availability may be partially responsible for the observed patterns.

Size and trends of the House Sparrow Passer domesticus population in Great Britain

House Sparrow Passer domesticus populations have declined throughout Europe over the last two to three decades; this is of particular concern in urban areas. We analysed data from extensive census schemes organized by the British Trust for Ornithology to determine the current population size of the House Sparrow in Britain, and to assess long‐term patterns of change, both in the wider countryside and in urban environments. The national breeding population of House Sparrows was estimated at approximately 13 million individuals (95% confidence interval, 11.9–14.8 million), or about six million pairs. Most of these occur in southeast England and densities are greatest in suburban and rural garden habitats. Overall, populations in rural areas have declined by 47% since the mid 1970s, whereas those in urban and suburban areas have declined by about 60%. Changes in farming practices are likely to account for at least some of the decline in the wider countryside, probably related to changes in food resources, with a loss of grain in fields and more secure storage of harvested grain, though these changes are unquantified. In urban areas, there was an earlier period of decline in the first half of the 20th century due to the loss of horse‐drawn transport and generally cleaner streets. The overall national decline since the 1970s masks much heterogeneity in trend among regional populations, and evidence suggests that population processes in the House Sparrow may be relatively fine‐grained.

Extra-Pair Paternity and Male Badge Size in the House Sparrow

Females of socially monogamous bird species frequently accept or solicit copulations with males other than their social mate. It has been proposed that in so doing females either gain direct benefits such as increased likelihood of fertilization in the event of their social mate being unable to provide sufficient sperm, or indirect (genetic) benefits for their offspring, e.g. 'good genes' from extra-pair partners of higher genetic quality than their own mate. Male ornaments such as elongated feathers and patches of coloured feathers are thought to act as visual cues to male quality. In this study we have used single-locus DNA profiling of two House Sparrow Passer domesticus populations to test the 'good genes' hypothesis prediction that males of low quality will be cuckolded most frequently. Both intraand extra-pair mate choice is influenced by the size of the male's black bib which may be indicative of male quality. Contrary to the 'good genes' prediction, small-bibbed males were not cuckolded more frequently in either population. Furthermore, none of the measured breeding parameters or female characteristics correlated with the occurrence of cuckoldry.