Fieldfare Research Articles

A comparative study of growth, skeletal development and eggshell composition in some species of birds

AbstractSome studies of birds suggest that the development of the skeleton may invoke a constraint on the rate of postnatal growth. Other studies have shown that the eggshell is the major source of calcium for skeletal development of the embryo. To test whether avian growth rate is indeed associated with different patterns of skeletal development, we compared the degree of skeletal ossification of the long bones of the wing and the leg of one slowly growing precocial species (quail Coturnix japonica) with that of two rapidly growing altricial species (starling Sturnus vulgaris and fieldfare Turdus pilaris). The degree of skeletal ossification of the long bones of the wings and legs of lines of quails that had undergone long‐term selection for high‐ and low‐growth rate, respectively, also was compared with a non‐selected control line. Next, the fine structure of the inner eggshell surface (mammillary layer) of both pre‐ and post‐incubated eggs, i.e. before and after embryonic development/calcium removal was compared. The data show that the skeleton of the more rapidly growing species and lines was less ossified than that of the more slowly growing ones. This difference appeared to be associated with different rates of calcium removal from the eggshell. Removal was more extensive in eggs of quail than in eggs of starling and fieldfare, i.e. more extensive in shells with a high number of mammillary tips per unit of surface area than in shells with a lower number. It is therefore concluded that growth rate is of fundamental importance for the pattern of skeletal development. Moreover, the mammillary density varies between different bird species, it is suggested, in order to support the different rates of calcium removal by developing embryos.

Explaining annual fluctuations in breeding density of fieldfares Turdus pilaris– combined influences of factors operating during breeding, migration and wintering

In a subalpine birch forest in Central Norway, the breeding population of fieldfare Turdus pilaris varied from 3 to 63 pairs per km2 during 1966–2000. For the period 1971–1995, the breeding density was negatively related to the number of days with >75% snow covered ground in April, presumably because snow cover reduce the availability of earthworms. In a multiple regression model for the period 1974–1995, snow cover in spring, the number of migrating fieldfares observed at two ornithological stations at the southern coast of Norway in April, the mean temperature in November in the preceding year, winter temperatures, rowanberry production in the previous autumn, and the interaction effect of the two latter variables (high value of one of these variables reduced the negative effect of a low value of the other) explained 80% of the variation in fieldfare breeding density. Autumn and winter temperatures, as well as rowanberry production, contributed through a positive effect, probably because these factors affected the number of fieldfare present in Norway throughout winter, which in some years may constitute a significant proportion of the overall fieldfare population.

Egg sizes of nine passerine bird species in a subalpine birch forest, Swedish Lapland

Egg measurements together with calculated volumes are presented for nine passerine species (Prunella modularis, Luscinia svecica, Phoenicurus phoenicurus, Turdus pilaris, Turdus philomelos, Turdus iliacus, Phylloscopus trochilus, Fringilla montifringilla, and Carduelis flammea), breeding in rich subalpine birch forests on a south-faced mountain slope in southern Swedish Lapland. There were no clear regional size trends in comparisons with egg collections from other parts of Europe. There was a significant increase in egg size in the latter part of the laying sequence. The ultimate egg is from 2.1% (F. montifringilla) to 6.5% (Ph. trochilus) larger than the mean of the clutch. According to several years’ measurements of T. pilaris and T. iliacus eggs there was no significant size variation between seasons. This constancy together with the relatively large egg sizes might be a consequence of the productive breeding habitat of the study area.

Latitudinal variation in the fruiting phenology of a bird-dispersed plant (shape Crataegus monogyna) in Western Europe

A number of fleshy-fruit-bearing plants of temperate regions are dispersed by migratory frugivorous birds. It has been suggested that the more southerly populations of such species should produce ripe fruits later than more northerly populations, to ensure that fruit is available when the birds arrive. I will call this the ‘adaptive delay’ hypothesis. To test this hypothesis, I monitored fruiting phenology of Crataegus monogyna Jacq. at ten sites (in all of which fruit consumption is very largely by redwings, Turdus iliacus, and fieldfares, Turdus pilaris) between northern Spain (42° N) and northern Scotland (59° N). There was no negative correlation between latitude and date of fruit ripening (earliest recorded date on which ripe fruits had appeared, or earliest recorded date by which all fruits had ripened). My results thus argue against the adaptive delay hypothesis.

Ligula intestinalis: interactions with the pituitary-gonadal axis of its fish host

I was delighted to be able to join with so many friends and colleagues, in writing this short paper to mark the retirement of Donald Lee. There are many outstanding milestones in Donald's career. However, I thought that I could perhaps draw special attention to his long and distinguished association with the British Society for Parasitology (BSP), and the journal, Parasitology. He was President of the BSP between 1978 and 1980 and, in recognition of his service to the Society and contributions to the discipline of parasitology, was elected an Honorary Member in 1980. Donald has also had a long association with Parasitology, as a member of the Editorial Board and as a frequent contributor. His first paper in the journal was published in 1958; it described the occurrence of Syngamus sp. in a fieldfare (Turdus pilaris) that had been accidentally killed. At the time of writing, his most recent publication, but I suspect not his last, was a biochemical study on proteins produced by Nippostrongylus brasiliensis, Nematodims battus and Ascaridia galli (Foster & Lee, 1996). Of course, Donald has published in many other journals and authored several books. However, if one considers only those papers published in Parasitology, they provide a record of intellectual vigour and curiosity that has remained undiminished throughout his career.

Do avian and mammalian nest predators select for different nest dispersion patterns of Fieldfares Turdus pilaris? A 15‐year study

The Fieldfare Turdus pilaris is an open‐nesting passerine that breeds either solitarily or in colonies. The nest‐spacing pattern of this species in a subalpine homogeneous Birch Betula pubescens forest in central Norway (c. 63°N) was studied during the period 1980–1994. Nest‐spacing patterns varied annually, and the number of Fieldfare colonies present (0–6) within a 3.5‐km2 study area was positively correlated with the annual density of small rodents and the birds' fat index and mean clutch size. After the rodent population crashes, prey switching seems to occur among mustelids. The nest‐spacing pattern of Fieldfares in the Birch forest therefore provides indirect support for the alternative prey hypothesis. Since the nest predation rate in Fieldfares is density dependent, and since their use of ejected faeces in communal defence may be detrimental, even lethal, to avian but not mammalian predators, it is suggested that a high density of mustelids results in selection for solitary breeding, whilst a predominance of avian predation risk selects for colonial breeding by the Fieldfare. The physical condition (fat index) of the Fieldfares is apparently a contributing factor in determining their nest dispersion pattern. The proportion of colonial nesting pairs was negatively correlated with the Fieldfare density and indicated a distributional pattern in a patchy habitat in agreement with the ideal free distribution theory.

FieldfareTurdus pilarisringing recoveries during autumn, winter and spring, analysed in relation to river basins and watersheds in Europe and the Near East

Fieldfare ringing data from 16 breeding zones in Europe and Asia were analysed in relation to autumn/winter recoveries in 15 western European and Jive Near East watershed areas. First year birds migrate several weeks later and to more regular destinations than adults. TWo watersheds, Maas/Schelde/Somme and Thames/ Humber, attract first year migrants from north and west Scandinavia. The Rhone/ Languedoc attracts first year migrants from Switzerland and Germany. The Po/ Upper Adriatic watershed is attractive to first year migrants from eastern Europe, north‐eastern Scandinavia, Russia and Siberia. Adults usually migrate further than first year birds and as a result are found in particularly high concentrations in Gironde/Adour. However, Central Russian and Siberian adults may winter much closer to their breeding areas, in the Aegean basin or the Transcaucasus. It is argued that this shows that adults are exploring more “exotic” destinations after their “preprogrammed” first year migration. The species favou...

Natural Selection of Colony Size in a Passerine Bird

1. The breeding success of fieldfares Turdus pilaris was studied in 56 colonies and 16 solitary pairs in a mountain birch area of N Sweden, and in 40 colonies and 70 solitary pairs in S Sweden. The analysis is based on a statistical method that treats colonies, not nests, as independent sample units. 2. The probability of adult survival was the major difference between the areas. Adult breeding birds ran a much higher risk of predation in S than in N Sweden; the risk increased with colony size. 3. Predation on eggs and nestlings decreased with increasing colony size in both areas. 4. The total risk of offspring loss owing to predation (of either parents or offspring) decreased with increasing colony size in the north, but not in the south

Dynamics of a passerine bird community in a small deciduous wood, S Sweden, during 40 years

The passerine bird community of a 13 ha nature reserve, consisting of a narrow valley with deciduous woods and open areas, was censused yearly from 1953 through 1992 by territory mapping. Its size, showing no significant trend, was on average 124± 15(SO) territories, belonging to 20±2 species. The community has fluctuated significantly (range 103 to 158, CV=12%). Its stability was founded on the restricted fluctuations of the most abundant species. Out of the 39 stationary species, 19 (=95% of the community size) appeared there for more than 20 years, only 8 of which have been yearly present. Fringilla coelebs, Phylloscopus trachilus, Sylvia borin, and Luscinia luscinia were the most abundant species throughout. Emberiza hortulana, Carduelis cannabina, and Anthus trivialis disappeared, while Sturnus vulgaris, Sitta eurapaea, Carduelis chloris, and Turdus pilaris immigrated. The species turnover rate between successive years was 21.7±9.7%, the long-term rate being about 1%. The community structure changed gradually: taken together, the population sizes of residents and short-distance migrants increased, from 38 to 57% of the community size; the tropical migrants declined correspondingly. These two species groups showed an opposing and significant covariation.

An Experimental Test of Optimal Clutch Size of the Fieldfare; With a Discussion on Why Brood Parasites Remove Eggs When They Parasitize a Host Species

The aim of the present study was to test the Incubation limit hypothesis; this states that the probability of hatching decreases when the number of eggs in a clutch increases above a certain limit. The results of this study indicate that experimentallyenlarged Fieldfare Turdus pilaris clutches had a relatively lower hatching success than natural-sized ones. The experimental clutches were 1.56 larger than natural clutches. This resulted in a 8% reduction in the relative hatching success for this experimental group compared with natural-sized clutches. Increasing the natural clutch size seems to have a negative effect on the relative hatching success of the Fieldfare in two ways: (1) eggs remaining unhatched, and (2) eggs becoming broken due to wear and tear during the incubation period. The results of this study therefore support the Incubation limit hypothesis. This hypothesis is also discussed in relation to the question whether brood parasites remove one or more host eggs in order to increase the hatching probability of the parasite's own egg.

Winter bird communities in woodland in the Forest of Dean, England, and some implications of livestock grazing

Winter bird communities, sampled by transect methods, were compared between 9 woodland sites (1 ungrazed oak, 4 grazed oak, 4 grazed conifer) in the Forest of Dean Gloucestershire, during 2 winters (1984/85 and 1987/88). Ungrazed oak woodland had the highest counts of individual birds in both years. More species occurred in oak woods than in conifers. Ordination of the combined data from the 2 winters illustrated a consistent gradient of bird species composition (after the exclusion of 2 flocking species, Woodpigeon and Chaffinch), from evergreen coniferous to deciduous broadleaf. Green and Great-spotted Woodpecker, Hawfinch, Field fare, Brambling, Great Tit, Magpie and Siskin occurred largely towards the deciduous broadleaf end of the gradient. Classification of the bird data split the sites firstly into deciduous broadleaf and evergreen coniferous. In further sub-divisions, one group had tree species composition consisting largely of ungrazed oak for which the indicator bird species was Hawfinch. The in...

Economics of Experimentally-Induced Territorial Defence in a Gregarious Bird, the Fieldfare Turdus pilaris

Fieldfares wintering in eastern England have a flexible social structure ranging from highly gregarious to near-territorial according to their food supply. Feeding experiments were carried out to investigate this variability. In experiments using apples, previously-gregarious Fieldfares established large exclusive territories, of a kind hitherto unknown in this species. Territory-owners spent more time on aggression and eating experimental apples and less time hunting invertebrates than non-territorial birds did. Within the range used, apple density and distribution had little effect on feeding and territorial behaviour. Increasing intrusion by Fieldfares and Starlings reduced the amount of time which owners spent eating apples, while increasing the time which non-territorial birds spent eating them. Increasing intrusion increased agonistic behaviour time for all birds. Estimated net energy gain of territory-owners declined with increasing intrusion rate while that of non-territorial birds did not. Territories shrank and were abandoned when non-territorial birds enjoyed higher net energy gain than owners, possibly following a period of assessment of the value of defence after defence had become uneconomical. Territoriality permitted accumulation of reserves in preparation for food scarcity and was thus part of an adaptation to unpredictable, rather than stable, food supplies.

Fieldfare Turdus pilaris Breeding Strategy: The Improtance of Asynchronous Hatching and Resources Needed for Egg Formation

Fieldfare Turdus pilaris Breeding Strategy: The Improtance of Asynchronous Hatching and Resources Needed for Egg Formation

Colonial and single breeding in fieldfares, Turdus pilaris L.: a comparison of nesting success in early and late broods

Pairs of fieldfares breed singly or in colonies. Their breeding season was subdivided into an early part, when the trees were still leafless, and a late part, when the trees had leaves. Early colonial pairs has a significantly higher nesting success than single pairs. However, amongst late broods the nesting success of both categories of pairs was the same. Colonies of only two pairs show a weak trend suggesting that it could be advantageous for early broods to have a neighbour nearby, while the nesting success of late broods seems to be highest if the neighbour is farther away. The number of neighbours is more important than the distance to the nearest neighbour when colonies of different sizes are examined. The nesting success of colonial broods is also influenced by the time of breeding. Success increases with colony size, in early colonies, but the opposite applies for the late breeding season.

Reproductive synchrony in the fieldfare (Turdus pilaris) in relation to spring arrival, nest predation and nestling starvation

In SW Sweden, solitary fieldfares (Turdus pilaris) were synchronized to the same degree as those living in colonies. In N Sweden, I investigated the degree of synchronization among colonies of varying size because solitary breeding occurred only occasionally. The degree of synchronization was not related to colony size. Synchronization was strongest in years when breeding started late and weakest in years when breeding commenced early. In N Sweden, the nest predation risk increased slightly as the season progressed. In SW Sweden, nestling mortality due to starvation was highest in early breeders, but their fledgling production exceeded that of late breeders. Increased nest predation penalized late layers.

Colonization of Islands by Land Birds: Prevalence Functions in a Finnish Archipelago

Land birds breeding on forty-four islands (size range 0.5-582 ha) in the Vargskar archipelago of the kland Islands (SW Finland) were censused in three (or two) breeding seasons in 1976-80 by one-visit methods. The islands were divided into five size classes and expected population sizes of land birds were estimated on the basis of (1) habitat composition of the islands and (2) population densities of each species in equivalent habitats in the source area, Main Aland. Prevalence is defined as the ratio between observed and expected population sizes. Observed densities of most of the fifty-six species studied did not deviate from expected values. Eleven species were more abundant on the islands than expected, including dominant generalists and species favoured by edges and bushy, heterogeneous habitat structure. Fourteen species had smaller populations on the islands than expected, but only seven of them consistently so in all census years and all island size classes. Habitat micro-structure seems important for three low-prevalence species, nest predation is invoked in two cases, in one case poor wintering capability seems a plausible factor, while one case remains obscure. Rarities were observed in the island censuses about as frequently as on Main Aland. Interspecific competition seems a plausible explanation for the absence of one species from the archipelago. One species, Turdus pilaris, changed its prevalence pattern dramatically in the study area by disappearing from the archipelago after the exceptionally cold winter of 1978/ 79; recolonization has taken place very slowly. The only species possibly showing density compensation is the dominant generalist Fringilla coelebs. Its populations on small islands are about doubled compared with the expecta- tions. Total densities are also higher than expected on small islands, but in most cases F. coelebs contributes less than half to the increase. In addition, there are no puzzling absences from small islands, but the poverty of their bird com- munities seems to result from reduced habitat diversity. Therefore autecological population responses rather than density compensation seem a plausible explana- tion of excessive population sizes of single species such as F. coelebs. We con- clude that, in these northern conditions, it seems appropriate to think of island communities as assemblages of species colonizing the islands according to their autecological (especially habitat) requirements. Ubiquitous habitat require- ments and flexibility in habitat utilization seem important correlates of coloniza-

Is nest predation really selecting for colonial breeding among Fieldfares Turdus pilaris?

IbisVolume 125, Issue 3 p. 366-369 Is nest predation really selecting for colonial breeding among Fieldfares Turdus pilaris? Olav Hogstad, Olav Hogstad Zoological Institute, University of Trondheim, N-7000 Trondheim, NorwaySearch for more papers by this author Olav Hogstad, Olav Hogstad Zoological Institute, University of Trondheim, N-7000 Trondheim, NorwaySearch for more papers by this author First published: July 1983 https://doi.org/10.1111/j.1474-919X.1983.tb03123.xCitations: 9AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume125, Issue3July 1983Pages 366-369 RelatedInformation

Costs and Benefits of Single and Mixed Species Flocking in Fieldfares (Turdus Pilaris) and Redwings (T. Iliacus)

1. Single species flocks of fieldfares and redwings tended to occur on different types of pasture: fieldfare flocks on new pasture ( < 4 years old) and redwing flocks on old pasture (25-400 + years old). Worms tended to be less abundant but were apparently easier to detect on new pasture. In single species flocks, fieldfares had a significantly higher capture rate and slightly high net rate of energy intake on new pasture than on old, but, on average, individuals of the two species had similar net rates of energy intake per gram body weight. 2. Fieldfare net rate of energy intake in single species flocks appeared to be a consequence of flocks size effects on time budgeting. Birds scanned less and crouched more in larger flocks. In redwings, however, there was no direct effect of flock size on individual feeding efficiency. 3. Mixed flocks almost always formed by fieldfares joining redwings on old pasture. One possible reason was the apparent drop in worm abundance on new pasture as the winter progressed. 4. Birds of both species had higher net rates of energy intake in mixed flocks than in single species flocks on old pasture. Fieldfares appeared to benefit directly from the presence of redwings and time budget analysis suggested that they used information from redwings about the whereabouts of prey, although the mode of interaction involved is not yet clear. The increased net rate of energy intake for redwings in mixed flocks, however, may have been due simply to increased worm abundance at the times mixed flocks formed.Zusammenfassung 1. Getrennte Fluge von Wacholder- und Rotdrosseln waren gew6hnlich auf verschie- denen Weidetypen zu finden: Wacholderdrosselfluge auf neuen Weiden (bis zu 4 Jahren alt), und Rotdrosselfluge auf alten Weiden (25-400+ Jahren alt). Auf neuen Weiden wa- ren im ganzen weniger Wurmen, aber scheinbar war es einf?cher, sie zu entdecken. Auf diesen Weiden gelangten die Wacholderdrosseln zu signifikant h6heren Fangziffern und einer etwas h6heren Reinziffer von Energieaufnahme als auf alten Weiden. Im Durch- schnitt aber hatten Einzelv6gel der zwei Arten dhnliche Reinziffern von Energieaufnahme per Gramm K6rpergewicht. 2. Es schien, dass die Gr6sse der Wacholderdrosselfluge die effektive Futterzeit und so- mit die netto Energieaufnahme beeinflusste. In gr6sseren Flugen suchten die V6gel weni- ger und hockten sie mehr. Nicht aber bei den Rotdrosseln, bei denen kein Einfluss der Fluggr6sse auf die wirksame Futterzeit gefunden wurde. 3. Gemisschte Flilge wurden fast immer durch Wacholderdrosseln geformt, die zich mit Rotdrosseln auf alten Weiden vereinigten. Eine m6gliche Ursache war eine Abnahme der Wurzelzahl auf neuen Weiden, die wahrscheinlich im Laufe des Winters auftrat. 4. V6geln von beiden Arten hatten in gemischten F16gen h6here Reinziffern von Ener- gieaufnahme als Vogel in Einzelffugen, die auf alten Weiden waren. Wacholderdrosseln schienen Vorteil von der Rotdrosselgegenwart zu haben, und eine Zeitrechnungsanalyse deutete an dass sie Information von den Rotdrosseln benutzen Cber die Stellung der Beu- te, obgleich die Mitteilungsweise noch nicht klar ist. Der h6heren Reinziffer der Energie- aufnahme von Rotdrosseln in gemischten Flugen k6nnte einfach eine gr6ssere Anzahl von Wurmern zugrunde liegen, zu dem Zeitpunkt, an dem die F16ge gebildet wurden.

Fieldfare (Turdus pilaris) breeding success in relation to colony size, nest position and association with Merlins (Falco columbarius)

Clutch size, nestling production and breeding success were studied in colonial Fieldfares (Turdus pilaris) in a subalpine birch forest during ten breeding seasons. Reproductive success was highest for central pairs in large colonies; such pairs benefited most from communal defence against nest predators. Fieldfares and Merlins (Falco columbarius) usually bred in association. Fieldfares breeding away from Merlins had lower breeding success than pairs associated with Merlins, which also benefited by reduced nest predation. Fieldfares apparently chose to nest near Merlins, which had already laid eggs when the thrushes started nest-building.

Clutch Size, Nest Size, and Hatching Asynchrony in Birds: Experiments with the Fieldfare (Turdus Pilaris)

Breeding strategy of an open—nesting passerine bird, the Fieldfare (Turdus pilaris) was studied in a woodland in Norway during four successive breeding seasons. Most birds laid clutches of five or six eggs; only 1% laid more than six. For 100 nests, eggs and/or chicks were added to raise the final number to seven hatchlings. Parents that laid a clutch of five eggs showed a equal skill in raising broods of seven, as did those who laid six. In enlarged broods, when only small age differences existed among the hatchlings, their survival rate was higher than that of enlarged asynchronous broods. In the enlarged synchronous broods the nestlings the subsequently died did so at a greater age than did those in the asynchronous broods. Brood size frequency for synchronous broods, recorded 8 d after brood enlargement, deviated from that expected under a random mortality pattern, i.e., mortality more resembled in "all—or—one" type. Hatching success was not lower for larger clutches (provided that the eggs hatched synchronously); the parents showed great skill in raising enlarged broods, and these nests were not subjected to a much greater degree of predation than were nests that contained small clutches and broods. The Fieldfare therefore normally rears a smaller—sized brood than could be nourished. More pairs that were provided with an artificial, large—sized nest managed to raise a brood of seven than did pairs that attempted to rear seven in their own original nest. Brood reduction in birds may not be adaptive, as argued by Lack and others, but may result from overcrowding. The reason why wider nest cups are not built in nature may be related to problems involved in hatching the eggs successfully; hatching losses were greater in enlarged nests than in natural nests.