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The costs and benefits of dominance status have been investigated in the past and it has generally been reported that subdominant birds are at a nutritional disadvantage owing to their low dominance status. The nutritional condition of birds during winter can be important in determining their likelihood of survival. This is particularly so in small passerines that are sensitive to severe weather conditions. Ptilochronology is an accurate method used to produce a long-term estimate of body condition spanning the number of days that it takes to grow a new feather. Ptilochronology was used during this study to estimate the nutritional condition of Coal Tits Pares ater during one winter and how condition was affected by dominance status. Dominant Coal Tits produced poorer quality feathers, which they grew at a slower rate, than did subdominant conspecifics. This study highlights a nutritional cost to high dominance status that could have long-term consequences because the induced tail feathers will not be replaced for at least 5 months.

We studied the role of early developed phenotypic characters associated to body size (i.e., tarsus, wing, and tail length) together with body mass in the determination of the winter residence and r...

The probability of perception of prey may depend on the previous experience of the predator, its expectations and its search tactics. In this study we investigated the role of the search area. Based on previous results and on known facts about foraging ecology, we hypothesised that crested tits ( Parus cristatus ) would perform better when searching larger areas for cryptic prey compared with coal tits ( Parus ater ) that have been found to search small areas for cryptic prey more successfully. In our experiments these two tit species were required to search for cryptic prey in large and small dishes. Both species detected cryptic prey less frequently in the larger dishes, however, crested tits performed better initially. Coal tits improved over time. Both species needed more time for detecting prey in large dishes, and crested tits searched longer in small dishes than coal tits. Giving-up times, when no prey was found, also reflected these differences. The results suggest that the tits search with speciesspecifically set search areas and 'time windows'. It also appeared that coal tits are more flexible in adjusting search to a given situation.

Possible biases related to the use of recordings were assessed by comparing captures of Coal Tits Parus ater with mist nets in presence and absence of tape lures. Samples netted with and without tape lures differed in age composition but not in body size. Moreover, tape lured nets caught resident birds less frequently than expected. Group size of flocks captured with the use of recordings was larger than those captured without. Tape lured juveniles had higher levels of subcutaneous fat reserves than Coal Tits captured at random, whereas this difference was not detected in adults. Attraction of dispersing juveniles and habituation to the tape lure by more resident individuals seemed to explain the patterns observed. Caution and knowledge of the biases caused by decoys is recommended before designing bird population studies which rely on the capture of birds by this method.

Sexual dimorphism of 2 plumage features and some morphological measurements was assessed in a sample of 140 museum skins and over 300 wild-trapped Coal Tits Parus ater britannicus. All the characters examined displayed highly significant sexual dimorphism, and have allowed the presentation of a recommended methodology which should allow over 90% of all British Coal Tits to be sexed correctly by fieldworkers. The validity of year-round sexing using characteristics of the throat feathering is proven by comparison with the results of a molecular DNA sexing technique.

Abstract. Two playback experiments were carried out to test the prediction on coal tits that singing rate could be used to assess the vigour of rival males, and that song length might be used in the same way, during singing interactions. Playbacks of songs with increasing rate inhibited the songs of responding birds, but induced more calls in response. The results suggested that a bout of singing with increasing rate is reacted to as a more serious threat than one with decreasing song output. The playback of long songs induced a greater number of calls in response, while fewer were produced during playback of shorter songs. The results suggest that a bout of long songs is responded to as a more serious threat than one of short songs.

The performances of the coal tit (a food storer) and the great tit (a non-storer) were compared in two experiments in which the bird was rewarded in phase 2 of a trial for returning to sites where it had seen food in phase 1 (‘window-shopping’). In both experiments the differences in performance between the species were small. In the first experiment the storing species was better than the non-storer at returning to the site where it had seen a seed, and in the second experiment the storing species was better at discriminating in phase 2 between sites visited in phase 1 that contained a seed and sites visited in phase 1 that were empty. A third experiment demonstrated that the motivational variables of reward size and deprivation were unlikely to account for the difference between the species. The results might indicate that there are differences in the spatial memory of the storing and non-storing species, but a difference in perceptual discrimination cannot be excluded.

We compared food-storing tits' memory for the locations of items they had stored and of food they had only seen. The results are consistent with suggestions that memory for stored food is subserved by the same memory system as that for encountered food

In a dominance-structured flock, social status may determine priority of access to food. Birds of low social status may perceive present and future access to food as less predictable, and so have a higher risk of starvation, than birds of high social rank. Theoretical models predict that subordinate birds should carry larger fat reserves and incur higher mass-dependent costs than dominants. However, empirical tests of the assumptions of these models are still scarce and controversial. We investigated the effect of dominance rank on daily mass gain under conditions of fluctuating food availability in a laboratory experiment using four flocks of four coal tits (Parus ater) each. The same amount of food was delivered in two treatments, but in one treatment the food was offered at a constant rate between days (fixed treatment), while in the other treatment the daily food supply varied in an unpredictable sequence between days (variable treatment). All birds showed greater variance in body mass in the variable treatment than in the fixed treatment. Body mass within birds showed the same variability at dawn than at dusk in the fixed treatment, but less variability at dawn than at dusk in the variable treatment. This may be a mechanism to reduce the immediate risk of starvation at the beginning of the day, when fat reserves are at their lowest and the aggression between flock members when feeding highest. Subordinate birds were excluded from the feeders by dominants more often in the early morning than in the rest of the day, and they showed more variability in daily mass gain and body mass at dawn than dominant birds. These results support the hypothesis that subordinate birds have a reduced probability of surviving when food availability changes unexpectedly compared to dominants., This study was funded by DGCYT project PB95-0102-CO2-01 of Ministerio de Educación y Cultura (MEC, Spain)

Current theory of risk-sensitive foraging predicts that foragers should choose feeding sites on the basis of variation in as well as mean reward rate when there is a shortfall in their food supply or a decrease in their energy budget. For a given mean reward delay, they should choose high variance feeding sites if they are running below energy requirement, but low variance sites if they are running above. It has been suggested that the smaller the animal size, the stronger the preference reversion between high and low variable feeding sites. Previous tests of the energy budget rule when there was time variability have used bird species heavier than 80 g. Hence we tested energy budget rule predictions with coal tits Parus ater, a bird of 9 g of body mass, foraging at two feeding sites with high or low variability in food delivering delay. We manipulated energy budgets by controlling air temperature in the laboratory. In one treatment (positive budget), individuals were allowed to eat at the level of their own ad-libitum daily consumption and the air temperature was set to 24°C, while for the other treatment (negative budget), temperature was set to 14°C, and food availability was limited to the maximum daily intake observed in the positive budget treatment. When air temperature was low, daily intake increased but body mass decreased. Birds were also less active in the low temperature treatment, hopping less times every day. Latency to peck decreased as well, pecking for food when it was available sooner than in the high temperature treatment. These results show that coal tits were living in a negative energy budget when air temperature was set to 14°C. Preference for the variable feeding site was greatest in the negative energy budget, as it was predicted by the energy budget rule. Contrary to the energy budget rule, coal tits consistently preferred the variable option also in the positive energy budget. Possible explanations for these results are explored, including alternative foraging models to the energy budget rule.

Theoretical models predict that birds should decrease their body mass in response to increased predation risk because lighter birds take off faster and are more manoeuvrable. We studied the effect of predation risk by chasing coal tits in large outdoor aviaries thus simulating an attempt to capture them. With this increase in predation risk, both perceived and actual, coal tits lost significantly more weight than in a control situation when they were not pursued. This pattern was attributable to a smaller gain in weight only during the day; nocturnal weight did not change in relation to diurnal predation risk. The lower daily weight gain was not consistent with predictions from models of interrupted foraging, but was consistent with predictions from risk adjustment models. Moreover, there was no difference in weight gain over 2-h periods that included a 1-h fast and those in which feeding was ad libitum, suggesting that coal tits could easily regain their body mass after a predator had interrupted their feeding. Our results therefore suggest that pursuit by predators leads to a decrease in the body mass of small birds. Copyright 1999 The Association for the Study of Animal Behaviour.

We compared the ability of coal tits, Parus ater (a food-storing species), great tits, P. major, and blue tits, P. caeruleus (two nonstoring species) to remember spatial locations in a spatial delayed-matching-to-sample task. Presentation of a single sample image on a touch screen was followed by a choice phase containing two, three or four images, in which the bird had to choose the original image. Storers made more correct choices than did nonstorers. Performance was affected by the proximity of the distractors: both groups performed less well when distractors were close to the sample although storers were less affected by proximity of distractors than were nonstorers. Both groups made correct decisions sooner than errors. We conclude that the accuracy of spatial memory in food-storing birds is greater than that of nonstorers. Copyright 1999 The Association for the Study of Animal Behaviour.

Many studies of tit populations (Parus spp.) have been carried out over many years in Europe. In these studies different aspects of tit biology have been analysed in an ecological and evolutionary perspective. The extension to Portugal of such studies which were developed long ago in the atlantic and mediterranean contexts may bring new and interesting insight to the analysis of existing data.

Gosler, A. G. & King, J. R. 1989. Asexually dimorphic plumage character in the Coal Tit Parus ater with notes on the Marsh Tit Parus palustris. Ring. & Migr. 10: 53–57. Although Coal Tits may be sexed during the breeding season on the presence or absence of a brood patch or cloacal protruberance, no plumage differences have been noted previously, so that sexing has not been possible outside this period. We present observations of Coal Tits trapped at two sites in southern England which indicate that the bib of this species is strongly dimorphic in shape, extent and colour intensity.

The state of greater covert moult in 145 first winter Coal Tits Parus ater from 5 suburban English sites was examined. There was a statistically significant difference between sites in the number of greater coverts moulted, with a tendency for birds from more northerly and easterly sites to have more old, unmoulted greater coverts than birds from more southerly sites. The results could not be fully explained by variations between seasons in the number of greater coverts moulted or in the relative proportions of birds from second broods. The possible effects of habitat differences are discussed and it is suggested that birds from more northerly areas may moult fewer greater coverts as an energy conservation measure.

The aim of this study was to reveal the causes and consequences of individual differences in foraging behaviour of coal tits, Parus ater, on the island of Gotland in the Baltic. On Gotland the willow tit, P. montanus, and the crested tit, P. cristatus, are absent, while these larger species are abundant competitors on the mainland. The Gotland population of coal tits exploited parts of the foraging niches of their absent competitors. Gotland coal tits are bigger than those on the mainland; they have thus evolved towards the size of the missing competitors. Individual differences in niche use were related to their morphology. Large birds more often used the inner parts of trees whereas small individuals foraged more on needles in the outer parts of the trees. Also, individuals with wing shapes more suitable for hovering and slow flight foraged more on needles. It is argued that morphology affects the profitability of different foraging sites. However, for foraging site selection, age was more important than morphology. Older, and probably more dominant, individuals occupied the most profitable foraging sites.

In Europe, coal tits (Parus ater) are found mainly in conifer woods, while blue tits (Parus caeruleus) live predominantly in broad-leaved trees (Snow, 1954). It has been suggested (Lack and Southern, 1949) that the blue tits (P. caeruleus teneriffae) of La Palma and Tenerife, Canary Islands, are convergent in an evolutionary sense with European coal tits as a result of life in conifer habitats. This suggestion was based on the habitat similarity and on the morphologies of the birds: the European blue tits have short stubby beaks (see Table 1), while the European coal tits and Canary Island blue tits have long thin beaks. Lack and Southern argued from this evidence that the similarity in bill shape of Tenerife and La Palma blue tits and European coal tits may be interpreted as convergence because of life in similar conifer habitats. They suggested that convergence in bill shape might be attributable to similar feeding methods or foods. In this paper we will describe the feeding methods of the blue tits on Tenerife and La Palma during the months of March and April, 1974, and for a short period in July, 1974. The data were collected to determine whether these birds feed in a similar way to English coal tits, and hence whether their bill shape could be adapted to conifers in the same way. We will also describe some laboratory experiments on the feeding skills of two Tenerife blue tits, and compare them with English blue and coal tits feeding in the same situation. The