Allan Carlson

The search cost in mate choice of the pied flycatcher

Alcock, J. 1973. Cues used in searching for food by redwinged blackbirds (Agelaius phoeniceus). Behaviour, 46, 174-188. Anderson, J. 1980. Cognitive Psychology and its Implications. San Francisco: Freeman. East, R. & Pottinger, R. 1975. Starling (Sturnus vulgaris L.) predation on grass grub (Costelytra zeelandica White, Melolonthinae) populations in Canterbury, New Zealand. N.Z.J. Agric. Res., 18, 417-452. Feare, C. 1984. The Starling. Oxford: Oxford University Press. Hollis, K. 1982. Pavlovian conditioning of signal-centred action patterns and autonomic behaviour: a chronological analysis of function. Advances in the Study of Behaviour. Vol. 12 (Ed. by J. Rosenblatt, R. Hinde, C. Beer & M. Busnell), pp. l~a4. London: Academic Press. Johnston, T. 1982. Selective costs and benefits in the evolution of learning. In: Advances in the Study of Behaviour. Vol. 12 (Ed. by J. Rosenblatt, R. Hinde, C. Beer & M. Busnell), pp. 65-106. London: Academic Press. Kamil, A. & Yoerg, S. 1982. Learning and foraging behavior. In: Perspectives in Ethology. Vol. 5 (Ed. by P. Bateson & P. Klopfer), pp. 325-364. New York: Plenum Press. Miller, R., Tamm, S., Sutherland, G. & Gass, C. 1985. Cues of orientation in hummingbird foraging: color and position. Can. J. Zool., 63, 18-21. Tinbergen, J. 1976. How starlings (Sturnus vulgaris L.) apportion their foraging time in a single-prey situation on a meadow. Ardea, 64, 155-170. Tinbergen, J. 1981. Foraging decisions in starlings (Sturnus vulgaris L.). Ardea, 69, I~i7. Tinbergen, J. & Drent, R. 1980. The starling as a successful forager. In: Bird Problems in Agriculture (Ed. by E. Wright, I. Inglis & C. Feare), pp. 8347. Croydon: British Crop Protection Council.

Biometry, habitat distribution and breeding success in the Pied Flycatcher Ficedula hypoleuca

Pied Flycatcher Ficedula hypoleuca Pall. populations in deciduous and coniferous habitats around Uppsala, Central Sweden, were compared. In deciduous as compared to coniferous habitat, males, but not females, were larger, territories were occupied and egg laying started one week earlier, and final breeding success was higher. The size-related assortment of individuals upon the two habitats was interpreted as the outcome of competitive interactions. This finding and the lower reproductive success in the less preferred habitat are in accordance with Fretwells ideal despotic distribution model.

The effect of habitat loss on a deciduous forest specialist species: the White-backed Woodpecker (Dendrocopos leucotos)

Abstract The White-backed Woodpecker (Dendrocopos leucotos), one of the rarest European woodpeckers, is an old-growth deciduous forest specialist which has shown widespread decline over most of its distribution range. In this study, I extend earlier analyses concerning range contraction and explore whether there exists a threshold in the amount of suitable habitat below which the species will not persist, and if there is a nonlinear decline in population size as suitable habitat in the forest landscape is reduced. A metapopulation model was parameterized with data from a stable population and an analytical estimated extinction threshold was tested on two data sets on population decline and range contraction. The species disappears from regions when the amount of deciduous forest declines below a certain level. One isolated Swedish sub-population, which had withdrawn to a forest-landscape with resources below the habitat threshold, became extinct in 1996. The two other Swedish sub-populations are in forest landscapes below the minimum habitat threshold and both these populations are declining. Finnish sub-populations persist in a landscape below the habitat threshold, however. Reanalyzing data for Finland indicates a time delay in population response as habitat is destroyed and when the amount of suitable habitat falls below 10% there is an accelerated decline in population size. In today’s intensively managed forests in Sweden and Finland, with low proportions of suitable habitat in the forest landscape, the immediate danger for the species is that the population will suffer from isolation.

Extinction dynamics and the regional persistence of a tree frog metapopulation.

The concept of a metapopulation acknowledges local extinctions as a natural part of the dynamics of a patchily distributed population. However, if extinctions are not balanced by recolonizations or if there is a high degree of spatial synchrony of local extinctions, this poses a threat to and will reduce the metapopulation persistence time. Here we show that, in a metapopulation network of 378 pond patches used by the tree frog (Hyla arborea), even though extinctions are frequent (mean extinction probability pe = 0.24) they pose no threat to the metapopulation as they are balanced by recolonizations (pc = 0.33). In any one year there was a pattern of large populations tending to persist while small populations became extinct. The total number of individuals belonging to populations that went extinct was small (<5%) compared with those populations that persisted. A spatial autocorrelation analysis indicated no clustering of local extinctions. The tree frog metapopulation studied consisted of a set of larger, persistent populations mixed with smaller populations characterized by high turnover dynamics.

Tropical forest fragmentation and nest predation – an experimental study in an Eastern Arc montane forest, Tanzania

When a habitat becomes fragmented and surrounded by another habitat this generally causes an increase in predation pressure at habitat transitions, often referred to as an edge effect. Edge effect in the form of enhanced nest predation intensities is one of the most cited explanations for bird population declines in fragmented landscapes. Here, we report results from a nest predation experiment conducted in a tropical montane forest landscape in the Uzungwa Mts., Tanzania. Using artificial nests with chicken eggs, we determined predation rates across a fragmentation gradient. The proportion of indigenous forest in four landscapes used in the study were 0.29, 0.58, 0.75 to 1.0. Nest predation intensities on artificial nests were about 19% higher inside intact forest than at edges in fragmented forest landscapes. Furthermore, predation intensities were relatively constant across a forest fragmentation gradient. Our results thus challenge the applicability and generality of the edge effect, derived from studies almost exclusively conducted in temperate regions rather than tropical forest ecosystems. Nest predation levels differences between tropical montane forest and that reported in other forest ecosystems are discussed.

Biogeographic patterns of the East African coastal forest vertebrate fauna

The archipelago-like coastal forest of East Africa is one of the highest priority ecosystems for biodiversity conservation worldwide. Here we investigate patterns of species richness and biogeographic distribution among birds, mammals and reptiles of these forests, using distribution data obtained from recently published reviews and information collated by the WWF Eastern Africa Coastal Forest Ecoregion Programme. Birds and mammals species were divided into forest specialists and generalists, and forest specialist reptiles into ‘coastal’ and ‘forest’ endemics. The species richness of birds and generalist mammals increased with area, and is probably a result of area-dependent extinction. Only in birds, however, species richness increased with decreasing isolation, suggesting possible isolation-dependent colonization. Forest diversity, associated to altitudinal range, is important for specialist birds and mammals, whose species richness increased with wider altitudinal range. The number of relict coastal endemic and forest endemic reptiles was higher in forests with wider altitudinal ranges and on relatively higher altitude, respectively. Such forests have probably provided a suitable (and perhaps stable) environment for these species through time, thus increasing their persistence. Parsimony analysis of distributions (PAD) and cluster analyses showed geographical distance and general ecological similarity among forests as a determinant factor in bird distribution patterns, with compositional similarity decreasing with increasing inter-forest distance. Compositional similarity patterns of mammals among the forests did not show a strong geographical correspondence or a significant correlation with inter-forest distance, and those of reptiles were not resolved, with very low similarity levels among forest faunas. Our results suggest that the relative importance (and causal relationship) of forest attributes affecting the distribution of the East African coastal forest vertebrate fauna varies depending on life history traits such as dispersal ability and forest specialization. The groupings in PAD are partly congruent with some of the previous classifications of areas of endemism for this region, supporting the ‘naturalness’ of these regions.

Territory quality and feather growth in the White-backed Woodpecker Dendrocopos leucotos

and pair bond on the breeding success of Great Tits Parus major. Ibis 127: 306-315. Rowley, I. 1983. Re-mating in birds. In: Bateson, P. (ed.). Mate Choice. Cambridge University Press, Cambridge, pp. 331-360. Soler, M. and Soler, J. J. 1996. Effects of experimental food provisioning on reproduction in the Jackdaw Corvus monedula, a semi-colonial species. Ibis 138: 377-383. Sullivan, K. A. 1989. Predation and starvation: age-specific mortality in juvenile Juncos (Junco phaenotus). J. Anim. Ecol. 58: 275-286. Svensson, E. and Nilsson, J. A. 1995. Food supply, territory quality, and reproductive timing in the Blue Tit (Parus caeruleus). Ecology 76: 1804-1812. Sxether, B.-E. 1990. Age-specific variation in reproductive performance of birds. In: Power, D. M. (ed.). Current Ornithology, Vol. 7, Plenum Press, New York, pp. 251283.

Polygyny and Breeding Success of Pied Flycatchers Nesting in Natural Cavities

Many hole-nesting passerine birds accept, or even prefer, nest boxes. Hence most of our knowledge about the breeding biology, population dynamics, life-history evolution and so forth of such species comes from nest box studies. This, in some cases, might lead to erroneous conclusions. For example, breeding density in nest box areas may often be much higher than in the natural situation (e.g. von Haartman, 1971), possibly leading to unnatural density dependent effects. Furthermore, the use of nest boxes may reduce predation risks (e.g. Nilsson 1975, 1984 a,b, Moller 1989), while the routine procedure of cleaning boxes after each breeding season may reduce the number of parasites, thus affecting nest site choice, mate choice and reproductive success (Moller 1989).