Numerous explanations exist for the evolution of reversed size dimorphism in raptorial species. A recent study concluded that reversed size dimorphism in skuas and jaegers was probably not attributable to breeding-role specialization, but that there was evidence for sexual selection, and in particular intrasexual competition by females for males. Our study tested the applicability of those conclusions for Southern (or Brown) Skuas (Stercorarius skua lonnbergi) breeding in South Georgia. Clutch volume was related positively to size and condition of females and negatively to condition of males, but there was no evidence of assortative mating for size or condition within pairs. Potential explanations for the discrepancy between this and previous studies are that size is less closely correlated with individual quality because of highly diverse foraging strategies, territory quality is a confounding factor, or because lower aggression in Southern Skuas reduces the necessity for small females to avoid large males

Carr, Steven M.

Fraser, Gail S.

Jones, Ian L.

Rowe, Sherrylynn

Lessells, C.M.

Dingemanse, N.J.

Both, C.

University of Groningen Research Database

Egg weights, egg component weights, and laying gaps in Great Tits (Parus major) in relation to ambient temperature

Leisler, B.

Winkler, H.

Wink, M.

MPG.PuRe

Evolution of breeding systems in acrocephaline warblers

Stienen, Eric W.M.

Brenninkmeijer, A

University of Groningen

Foraging decisions of sandwich terns in the presence of kleptoparasitising gulls

Blomqvist, D.

Kempenaers, B.

Lanctot, R.

Sandercock, B.

Genetic parentage and mate guarding in the Arctic-breeding Western Sandpiper

Most obligate cavity-nesting birds are considered to be nest-site limited, either by time or energy to excavate or to acquire suitable holes for nesting. We examined rates of nest-cavity reuse for a rich community of cavity-nesting birds in mixed forests in interior British Columbia. Using a sample of 402 cavity-reuse cases over five years, we measured cavity reuse for 20 cavity-nesting bird and mammal species (three guilds), and examined the relationship between nest-cavity reuse and features of cavities, nest trees, and forest stands. Eight percent of used cavities were destroyed between years. Reuse rates were 17% for the cavities of weak excavators such as nuthatches and chickadees, 28% for formerly active woodpecker nests, and 48% for cavities previously used by secondary cavity nesting birds, but there was considerable species variation within all guilds. Nest cavities in aspen that were deep with large entrances had the highest reuse. At the forest stand level, cavities in trees close to edges and in sites with more edge habitat had greater reuse. Reused cavities tended to be occupied in sequential years rather than being inactive for a year. With increasing amounts of managed landscapes, availability of suitable cavities for forest nesting vertebrates is decreasing. Reuse of existing cavities might help mitigate the problem of nest-site limitation

Aitken, K.E.H.

Wiebe, K.L.

Martin, K.

DigitalCommons@USU

Nest-site Reuse Patterns for a Cavity-Nesting Bird Community in Interior British Columbia

Irwin, Darren

Irwin, Jessica

Lund University Publications

Circular overlaps: Rare demonstrations of speciation

We studied the early morning cage orientation of nocturnally migrating Swainson's Thrushes (Catharus ustulatus) during three fall migration seasons. The results were compared with earlier free-flight release tests under starry skies and were found to be consistent with continuation of migratory flights in the expected seasonally appropriate direction. Energetic condition proved decisive: fat birds chose directions in accordance with migration across the Gulf of Mexico, whereas lean birds oriented away from the coast, possibly in search of habitats suitable for refuelling. Whereas the orientation of fat Swainson's Thrushes was affected by experimental shifts of the magnetic field, the response during morning tests was larger than expected. A parallel series of orientation cage experiments performed during evening twilight showed a response to deflected magnetic fields that was close to the expected shift, which suggests a difference in integration of directional information between early morning and evening twilight activity. However, within-individual response to deflected magnetic fields was of the same magnitude during both morning and evening tests

Sandberg, Roland

Moore, FR

Bäckman, Johan

Lohmus, M

Orientation of nocturnally migrating Swainson's thrush at dawn and dusk: Importance of energetic condition and geomagnetic cues

The growing use of comparative methods to address evolutionary questions has generated an increased need for robust hypotheses of evolutionary relationships for a wide range of organisms. Where a phylogeny exists for a group, often more than one phylogeny will exist for that group, and it is uncommon that the same taxa are in each of the existing trees. The types of data used to generate evolutionary trees can also vary greatly, and thus combining data sets is often difficult or impossible. To address comparative questions for groups where multiple phylogenetic hypotheses already exist, we need to combine different hypotheses in a way that provides the best estimate of the phylogeny for that group. Here, we combine seven seabird phylogenies (based on behavioral, DNA-DNA hybridization, isozyme, life history, morphological, and sequence data) to generate a comprehensive supertree for the Procellariiformes using matrix representation with parsimony. This phylogeny contains 122 taxa and represents a conservative estimate of combined relationships presented in the original seven source trees. We compared the supertree with results of a combined sequence data supermatrix for 103 seabird taxa. Results of the two approaches are broadly concordant, but matrix representation with parsimony provides a more comprehensive and more conservative estimate of the phylogeny of the group because it is less influenced by the largest of the source studies (which uses a single, relatively quickly evolving gene). Genetic data sets that can be combined in a supermatrix approach are currently less likely to be available than phylogenies that can be combined using some form of supertree approach. Although there are limitations to both of those approaches, both would be simpler if all phylogenetic studies made both their data sets and trees they generate available through databases such as TREEBASE

Kennedy, M.

Page, R.D.M.

Enlighten

Seabird supertrees: combining partial estimates of procellariiform phylogeny

We studied prey selection of Sandwich Terns (Sterna sandvicensis) in the presence of kleptoparasitising Black-headed Gulls (Larus ridibundus) on Griend, Dutch Wadden Sea, from 1992 to 1998. Most often, gulls robbed larger sandeels rather than herring from terns. Provided that one parent attends the chick, energy intake would be too low for the chicks' survival if exclusively fed on sandeel. By provisioning an increasing proportion of herring, parent terns could theoretically overcome a potential food shortage when the chicks grow older. However, the proportion of herring did not increase with age of chicks in most years. Instead, parents increased their foraging effort with the growth of their offspring. In years with high proportions of food loss, parents left their chicks unattended at the nest more often. In that way, parents were largely able to counterbalance food shortage of offspring. In 1992 and 1996, when diet composition was unfavorable and food losses to gulls were high, parents left their chicks unattended at the nest for 680% of the daylight period. It is argued that the present working level of parents might be higher than in the 1960s

Stienen, E.W.M.

Brenninkmeijer, A.

Open Marine Archive

Foraging decisions of Sandwich Terns in the presence of kleptoparasitising gulls

Reproductive Biology and Behaviour Group

1103 Egg Weights, Laying Gaps, and Temperature

Avian Breeding Cycles.

Climate change and constraints on breeding.

Clutch size, intraclutch eggsize variation, and breeding strategy in the Goldcrest Regulus regulus.

Composition of the eggs of the Great Tit (Parus major) and the Pied Flycatcher (Ficedula hypoleuca). Annals Zoologica Fennici 20:57–63.

Composition of Wood Duck eggs in relation to egg size, laying sequence, and skipped days of laying.

Density dependent recruitment rates in Great Tits: The importance of being heavier.

Effect of heating nest boxes on egg laying in the Blue Tit (Parus caeruleus). Auk 110:95–99. Associate Editor:

Effects of laying sequence and ambient temperature on the composition of eggs of the Great Tit Parus major and the Pied Flycatcher Ficedula hypoleuca. Annals Zoologica Fennici 20:65–71.

Effects of population density and supplemental food on reproduction in Song Sparrows.

Egg dimensions of the Great Tit Parus major in southern Finland. Ornis Fennica 66:69–74.

Egg size variation within passerine clutches: Effects of ambient temperature and laying sequence. Ornis Fennica 58:93–108.

Egg size, hatching asynchrony, sex, and brood reduction in the Common Grackle. Ecology 57:1195–1207.

Eggs, egg formation and the timing of breeding.

Energetic limitation in the egg-laying period of Great Tits.

Food as a limit on breedingbirds: A life history perspective. Annual Review of Ecology and Systematics 18:453–487.

Food supplementation experiments with terrestrial vertebrates: Patterns, problems and the future.

Initial investment, clutch size, and brood reduction in the Common Grackle (Quiscalus quiscula L.). Ecology 59:1109–1122.

Intraclutch egg-size variation in birds: Physiological responses of individuals to ﬂuctuations in environmental conditions.

Intraclutch egg-size variation in the Eurasian Kestrel: Advantages and disadvantages of hatching from large eggs.

Intraspeciﬁc variation in egg size and egg composition in birds: Effects on offspring ﬁtness.

Is intraclutch egg-size varaition adaptive in the Lesser Snow Goose? Oikos 67:250–256.

On the adaptive value of intra-clutch egg-size variation in birds.

Population ﬂuctuations and clutch size in the Great Tit, Parus major.

Proximate factors affecting egg volume in sub-Arctic hole-nesting passerines. Ornis Fennica 68:99–104.

Quantitative genetics in natural populations of birds illustrated with examples from the Great Tit (Parus major). Pages 67–79 in Population Biology and Evolution (K.

Re-examination of the capital and income dichotomy in breeding birds.

Seasonal changes in egg-mass within and among clutches of birds: General explanations and a ﬁeld study of the Blackbird Turdus merula. Ibis 134:171–179.

Seasonal variation in local recruitment of Great Tits: The importance of being early.

Selection for the timing of Great Tit breeding in relation to caterpillar growthand temperature.

Temperature and foraging success of Great Tits Parus major hunting for spiders.

The effect of female body condition on egg laying in Lesser Black-backed Gull Larus fuscus.

The frequency and timing of laying gaps.

The level of reserve protein as the proximate factor controlling the timing of breeding and clutch-size in the Redbilled Quelea, Quelea quelea.

The timing of birds’ breeding seasons. Ibis 112:242–255.

Tits and their caterpillar food supply.

Unterbrechung der Legefolge bei Ho ¨hlenbru ¨tern.

Variation in egg size in Great Tits.

Variation in weight and composition of Brown-headed Cowbird eggs. Condor 87:296–299.

Variation in weight and composition of Red-winged Blackbird eggs.

Water and ionic ﬂuxes inside the egg.

When mothers prefer daughters over sons.