JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. The hypothesis that late breeding entails reproductive costs to birds was tested by comparing breeding traits of control and delayed great tit Parus major clutches. 2. In our study area, great tits and house sparrows Passer domesticus compete for nesting boxes. Since early March, nesting boxes were checked twice a week and initiated sparrow nests removed, to allow great tits to breed. 'Delayed' great tit pairs were those which, having a territory, had the nesting where they eventually bred occupied by sparrows, and therefore did not start laying until these abandoned the nesting box. Delayed pairs were assumed to be a random sample of the population. Age composition (1-year vs. older birds) and tarsus length did not differ between control and delayed birds. 3. In 1990-92, a total of 40 pairs had their breeding delayed, while 56 acted as controls. The mean laying date of delayed pairs was at least 10 days later than controls. 4. Delayed first clutches were smaller and took longer to hatch than controls, but mean egg volume did not differ between them. Fledging success was lower in delayed nests. Young from delayed broods were lighter at day 15 and reached a lower asymptotic weight. The mean growth rate of the nestlings was negatively related to clutch size, and differed between years, but did not differ between control and delayed broods. 5. Control pairs were more likely to produce a second clutch, if the first one succeeded, or a replacement clutch, if the first one failed, than delayed pairs. The total production of fledglings per pair per season was higher in control pairs. Control pairs were more likely to recruit at least one young into the local breeding population than delayed pairs. However, it is not known whether late fledglings dispersed further. 6. Our results show that delayed pairs produced fewer fledglings, of lower quality, and were less likely to recruit them into the local breeding population than controls. Therefore, the causal relationship between poor breeding performance and late breeding is supported.

No abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.

Plastic intake by marine vertebrates has been widely reported, but information about its presence in continental waterfowl is scarce. Here we analyzed faeces of waterbirds species (European coot, Fulica atra, mallard, Anas platyrhynchos and shelduck, Tadorna tadorna) for plastic debris in five wetlands in Central Spain. We collected 89 faeces of shelduck distributed in four lakes, 43.8% of them presented plastic remnants. Sixty percent of 10 faeces of European coot and 45% of 40 faeces of mallard contained plastic debris. Plastic debris found was of two types, threads and fragments, and were identified as remnants of plastic objects used in agricultural fields surrounding the lakes. Differences in prevalence of plastic in faeces, number of plastic pieces per excrement and size of the plastic pieces were not statistically significant between waterfowl species. Thus, our results suggest that plastic may also be frequently ingested by waterfowl in continental waters, at least in our study area. Future studies should address this potential problem for waterbird conservation in other wetlands to evaluate the real impact of this pollutant on waterbirds living in inland water.

No abstract

No abstract

Single-and multi-brooded species of birds differ in their seasonal patterns of clutch size. Single-brooded species start with a maximum clutch size that declines continuously as the season progresses, whereas the clutch sizes of multi-brooded species usually increase to a mid-season maximum peak and then decrease progressively until the end of the breeding season. Previous studies have shown that multi-brooded migrant species present seasonal patterns that are similar to single-brooded species at high latitudes but similar to multibrooded non-migratory species at lower latitudes. We studied the Greenfinch Carduelis chloris and Goldfinch C. carduelis populations in eastern Spain (Sagunto, Valencia) between 1975 and to compare seasonal variations in clutch sizes between years with early and late starts to the breeding season. The period over which clutch sizes increase was longer when the breeding season started earlier. The Goldfinch population showed no pattern of initial increase in clutch size when there was a late start to the breeding season: a late start shortens the season giving them less time to breed, and may also coincide with maximum food availability. Thus, the pattern of single-brooded species was observed. In the Greenfinch population, a trend toward the seasonal pattern of single-brooded species was also observed when the following indices were compared: clutch size increase, modal timing, initial slope and timing of maximum clutch size. We have also compared the seasonal patterns of clutch size of both species in eastern Spain with the patterns observed in Britain. Our results show that for both Goldfinches and Greenfinches, the non-migrant southern populations of Sagunto in eastern Spain do not tend towards a more multi-brooded seasonal pattern of clutch size than the migrant Goldfinches of Britain.Passerine birds use two tactics to maximize their number of offspring per breeding season. In singlebrooded species, the clutch size is at its maximum at the start of the breeding season and declines as the season progresses. Multi-brooded species, however, present a different pattern. Their breeding season is longer and females lay several clutches with a midseason peak of clutch size (Lack 1954, Klomp 1970. Therefore, in multi-brooded species, seasonal reproductive success is determined not only by the productivity of each brood but also by the number of broods raised (Bryant 1979, Desrochers & Magrath 1993. As a consequence, Crick et al. (1993) suggested that multi-brooded species start laying before the optimal moment, which accounts for the increase in clutch sizes until the optimal time, when clutch sizes are the largest. In addition, a tendency to start breeding earlier would be normal as it would allow a greater number of clutches per season. Furthermore, the same species might present both patterns across its distribution range if it is made up of non-migrant as well as migrant populations. The Eastern Bluebird Sialia sialis shows an initial increase in the size of clutches in the southern p...

Many European towns and cities have undergone reurbanisation processes in recent decades. However, their effects on urban biodiversity have been poorly studied. Currently urbanisation processes include park remodelling, which involves the replacement of semi-natural substrates (natural grass, bare soil) with artificial ones (pavement, concrete, areas for dogs, artificial grass). Our aim was to explore, for the first time, the effects of park remodelling on the trends and abundance of a declining urban exploiter, the House Sparrow. An abundance index of House Sparrows was obtained in 32 urban parks of four towns in the Valencian Community (Spain) in four summers (2015)(2016)(2017)(2018). Of the studied parks, 10 were remodelled during the study period. Before remodelling, the trends and abundance of House Sparrows in both groups of parks were similar and stable on average, which suggest no bias between both park groups. However, House Sparrow abundance was significantly reduced in parks affected by remodelling works while in those non-remodelled it remained stable. Park remodelling might be linked to a reduction in both habitat suitability and availability of trophic resources, which could harm urban House Sparrows populations and possibly other species as well. Therefore, new park policies and urban planning measures are urgently needed to preserve urban House Sparrows.