Scavenger Birds Chew The Fat

Humans aren’t the only ones who like fatty foods - bearded vultures do, too. A study by Antoni Margalida from the Bearded Vulture Study and Protection Group in El Pont de Suert, Spain, has found that the bearded vulture will discard less energy-dense bones and choose only the bones containing the highest fat content both for its consumption and delivery to its young.

Lees meer: Science Daily

Food shortages produce chick-killing auks

One of Britain's commonest auks is increasingly attacking and killing neighbouring chicks in response to food shortages at seabird colonies on a Firth of Forth island.

Researchers at the University of Leeds and the Centre for Ecology & Hydrology, who have been studying Common Guillemots on the Isle of May in Scotland, have observed a dramatic increase in the number of adults deliberately attacking chicks in neighbouring nests.


Lees meer: Birdwatch

Do small hole nesting passerines detect cues left by a predator? A test on winter roosting sites

Auteur(s): Ekner, A; Tryjanowski, P
Bron: ACTA ORNITHOLOGICA, 43 (1): 107-111; SUM 2008
Abstract: There are a lot of studies about relationships between prey and predators. However most have focused on the influence of lethal predators on their prey. We suggested that non-lethal effects may also be very important for a complete understanding of prey-predator interactions.
Among many influencing factors predation is important because it affects survival probability, especially in winter, which is a critical period for many passerines living in temperate zones. Apart from killing prey, predators may also have an indirect influence on the choice of nocturnal resting sites. Therefore, small passerines should detect and avoid places where a predator has operated previously. We tested this prediction using data on wintering small passerines, mainly on Great Tits.
The study was performed during the winter season of 2005/2006 in western Poland. In the experiment, we put fur and mangled feathers in half of 100 randomly selected nest boxes. Boxes were checked every ten days, from January-March. The birds showed a significantly stronger preference towards "clean" nest boxes (without predator traces). It seems that non-lethal predator influence modifies winter dispersion of birds and wintering passerines may detect, by Visual signals left behind, nest boxes where predation has previously occurred.

The establishment of an urban bird population

Auteur(s): Rutz, C
Bron: JOURNAL OF ANIMAL ECOLOGY, 77 (5): 1008-1019; SEP 2008
Abstract:
1. Despite the accelerating global spread of urbanized habitats and its associated implications for wildlife and humans, surprisingly little is known about the biology of urban ecosystems.

2. Using data from a 60-year study period, this paper provides a detailed description of how the northern goshawk Accipiter gentilis L. - generally considered a shy forest species - colonized the city of Hamburg, Germany. Six non-mutually exclusive hypotheses are investigated regarding the environmental factors that may have triggered this invasion.

3. The spatio-temporal analysis of 2556 goshawk chance observations (extracted from a total data set of 1 174 493 bird observations; 1946-2003) showed that hawks regularly visited the city centre decades before the first successful breeding attempts were recorded. Many observations were made in parts of the city where territories were established in later years, demonstrating that these early visitors had encountered, but not used, potential nest sites.

4. Pioneer settlement coincided with: (i) an increase in (legal) hunting pressure on goshawks in nearby rural areas; (ii) an increase in avian prey abundance in the city; and (iii) a succession of severe winters in the Greater Hamburg area. On the other hand, there was no evidence to suggest that the early stages of the invasion were due to: (i) decreasing food availability in rural areas; (ii) major habitat changes in the city; or (iii) rural intraguild dynamics forcing hawks into urban refugia. While breeding numbers of a potential rural source population were at a long-term low when the city was colonized, prior to first settlement there was a sharp increase of goshawk chance observations in the city and its rural periphery.

5. The urban population expanded rapidly, and pair numbers began to stabilize after about 10 years. Ringing data (219 ringed nestlings from 70 urban broods; 1996-2000) demonstrated that most urban recruits had fledged in the city, but also confirmed considerable gene flow between urban and rural habitats. Analysis of chance observations (as raw data or as detrended time series) suggested a tight coupling of population dynamics inside and outside the city.

6. City-colonizations such as the one described here provide a valuable opportunity to study some fundamental aspects of population ecology on a scale at which detailed monitoring is logistically feasible. Furthermore, a good understanding of urban ecology has become essential for efficient wildlife conservation in modern, human-altered environments.

French birds moving north too slowly

A new study of breeding birds in France has concluded that they are moving their range north more slowly than other effects of climate change that are influencing them.

Lees meer: Birdwatch / BBC News

Verdwijnen lemmingen ramp voor broedende ganzen

De Taimyr expeditie is weer terug uit Siberië. Van begin juni tot midden augustus onderzocht dit internationale onderzoeksteam van Alterra en het NIOO de relaties tussen pooldieren en de rol van het klimaat hierin.
Afgelopen zomer bleek rampzalig voor broedende ganzen. Een vroeg instortende lemmingenpopulatie veroorzaakte honger bij middelste jagers en sneeuwuilen, die hierdoor geen eieren legden en hun territoria niet verdedigden. Hierdoor gaven ze poolvossen vrije toegang tot het anders zo veilige broedgebied van de ganzen.
Ook Taimyrmeeuwen leden honger door het gebrek aan lemmingen en roofden ganzeneieren en –pullen. Tenslotte werden er veel rotgansnesten weggespoeld door grote hoeveelheden smeltwater.


Lees meer: Natuurbericht.nl