Emperor penguins face extinction

Emperor penguins, whose long treks across Antarctic ice to mate have been immortalised by Hollywood, are heading towards extinction, scientists say.

Based on predictions of sea ice extent from climate change models, the penguins are likely to see their numbers plummet by 95% by 2100.

That corresponds to a decline to just 600 breeding pairs in the world.


Lees meer: BBC News

Aggression and fitness differences between plumage morphs in the common buzzard (Buteo buteo)

Auteurs: M. Boerner, O. Krüger
Bron: BEHAVIORAL ECOLOGY 2009 20(1):180-185; doi:10.1093/beheco/arn132
Abstract: Genetic plumage polymorphism in birds is increasingly recognized as a potentially important trait influencing birds' life histories. In the common buzzard Buteo buteo, the 3 color morphs vary in lifetime reproductive success (LRS), but the proximate mechanisms leading to these differences are unknown. We first confirmed the stability of the fitness differences found previously, using a greatly extended LRS data set.
To find potential causes for these differences, we experimentally studied variation in aggressive behavior of the morphs, both against an interspecific predator and intraspecific competitors. The morphs showed substantial variation in aggressive behavior.
Light-colored males were most aggressive toward an interspecific predator, followed by intermediate and dark males. In females, this pattern was reversed, resulting in sex-related differences of aggression in 2 morphs. When defending their territory against intraspecific competitors, no absolute difference in aggression was found, but the morphs reacted strongest toward intruders of a morph similar to their own.
This suggests that aggression differs both between and within morphs, leading to a complex pattern on the population level. Coupled with the strong fitness differences, our results suggest that the genetic basis of the polymorphism has far-reaching behavioral consequences.

Lower annual fecundity in long-distance migrants than in less migratory birds of temperate Europe

Auteurs: Bruno Bruderer, Volker Salewski
Bron: JOURNAL OF ORNITHOLOGY, Volume 150, Number 1, pp. 281-286
Abstract: We use widely supported handbook data on annual fecundity (clutch size × annual number of normal broods) to obtain indications related to the relative costs of long-distance migration compared to lower levels of migratoriness. Our examples show that the yearly production of eggs in congeneric passerines of similar size from temperate Europe is lower in long-distance migrants than in their less migratory relatives.
The same tendency shows up in a more heterogeneous sample of non-passerines. In most passerines and in one among five pairs of non-passerines, this is due to longer breeding periods allowing a higher number of clutches in the less migratory species in spite of a tendency towards larger clutches in the passerine long-distance migrants.
If both migratory types have only one clutch (as in one species pair of the passerines and in four non-passerine pairs) the trend towards larger clutches was reversed between the two types.
The higher fecundity of the less migratory species suggests that wintering under harsh conditions may be more expensive than trans-Sahara migration among similar species. In keeping with this result, Ortolan and Rock Buntings (Emberiza hortulana and E. cia) breeding syntopically (and, in the 1980s, still in relatively stable populations) in an inner Alpine valley provide a well-studied example illustrating the high longevity of the migrants compared to the relatively short life span of the residents.

Causes, consequences and mechanisms of breeding dispersal in the colonial lesser kestrel, Falco naumanni

Auteurs: Joaquín Ortego, Pedro J. Cordero, José Miguel Aparicio
Bron: ANIMAL BEHAVIOUR, Volume 76, Issue 6, December 2008, pp. 1989-1996
Abstract: Dispersal is a common phenomenon in animals, with important consequences for individual fitness and the genetics and structure of populations. We studied the causes and consequences of breeding dispersal from an individual perspective using as a model organism the colonial lesser kestrel.
For this purpose, we gathered information on 235 birds that attempted to breed in 2 consecutive years (2004–2006) in any of the 22 colonies monitored in the study area. Eighty-two per cent of kestrels returned to the same breeding colony where they had attempted to breed in the previous year. Probability of dispersal decreased with age and individual reproductive performance in the season previous to dispersal and females dispersed more frequently than males. Dispersers settled in colonies with a higher mean reproductive performance than other available colonies located around their colony of origin. However, the size of the colony selected did not differ between selected and surrounding colonies.
Thus, dispersers selected highly productive rather than large colonies. Own body condition or the quality of the mates obtained (estimated by their pectoral thickness and size) did not change for individuals that dispersed or for philopatric individuals in subsequent seasons.
Although dispersers greatly increased their own breeding performance after dispersal, it did not exceed that of their philopatric counterparts. These results help to explain the coexistence of dispersal and philopatric behaviours within a population and suggest that dispersal may be an adaptive behaviour that increases reproductive performance, particularly for individuals that have suffered a bad breeding experience.

The onset of spring and timing of migration in two arctic nesting goose populations: the pink-footed goose Anser bachyrhynchus and the barnacle goose Branta leucopsis

Auteurs: Tombre, Ingunn M.; Høgda, Kjell A.; Madsen, Jesper; Griffin, Larry R.; Kuijken, Eckhart; Shimmings, Paul; Rees, Eileen; Verscheure, Christine
Bron: JOURNAL OF AVIAN BIOLOGY, Volume 39, Number 6, November 2008, pp. 691-703(13)
Abstract: An earlier onset of spring has been recorded for many parts of Eurasia in recent decades. This has consequences for migratory species, both in changing the conditions encountered by individuals on reaching migratory sites and in affecting cues regulating the timing of migration where decisions to migrate are influenced by local environmental variables. Here we examine the timing of spring migration for two arctic goose populations, the pink-footed goose Anser brachyrhynchus (during 1990-2003) and barnacle goose Branta leucopsis (during 1982-2003), which both breed on Svalbard. The satellite-derived Normalised Difference Vegetation Index (NDVI) was used to express the onset of spring at their wintering and spring staging sites.

Pink-footed geese use several sites during spring migration, ranging from the southernmost wintering areas in Belgium to two spring staging areas in Norway, and distances between sites used along the flyway are relatively short. There was a positive correlation in the onset of spring between neighbouring sites, and the geese migrated earlier in early springs.

Barnacle geese, on the other hand, have a long overseas crossing from their wintering grounds in Britain to spring staging areas in Norway. Although spring advanced in both regions, there was no corresponding correlation in the timing of onset of spring between their wintering and spring staging sites, and little evidence for barnacle geese migrating earlier over the whole study period.

Hence, where geese can use spring conditions at one site as an indicator of the conditions they might encounter at the next, they have responded quickly to the advancement of spring, whereas in a situation where they cannot predict, they have not yet responded, despite the advancement of spring in the spring staging area.