Retrieval of stored seeds by Marsh Tits Parus palustris in the field

The retrieval of stored food by Marsh Tits was documented using Hall-plate detectors to register visits to storage sites by marked individuals. In each experimental session a marked bird was allowed to store up to 50 radioactively labelled half-peanuts. By placing detectors next to each stored item that we located it was possible to show that birds attempt to retrieve about 25% of their stored food. Most of the retrieval is within one or two days (confirming Cowie et al. 1981) and the proportion of recorded retrieval attempts that are successful declines to zero after about three days. By this time storage sites have already been emptied by cache robbers. There may be a tendency for retrieval to occur in the afternoon.     

One Norwegian territory of the Marsh Tit Parus palustris during 35 years

One Norwegian territory was occupied by successive pairs of Marsh Tits Parus palustris during 35 breeding seasons. Only ten males and seven females were involved. Each pair showed strict site fidelity and kept to the territory all year round. The pair bond lasted throughout life, and the duration varied from one to eight successive years. The number of successive mates varied for the males from one to two females and for the females from one to four males. Assuming that the birds were juveniles or 1 year old when ringed, they survived, on the average, 4.4 years. The oldest male survived for at least 10 years 4 months and the oldest female for 8 years 4 months. The mean survival rate of adults from one breeding season to the next was 75.8%, which is remarkably high when compared with the genera! findings in tits.     

Advantages of social foraging of Willow Tits Parus montanus

The mean number of Willow Tits Parus montanus in single-species flocks was significantly larger than in mixed-species flocks of Willow and Coal Tits P. ater. Both flock size and the tendency of Willow Tits to join mixed-species flocks were negatively correlated with ambient temperature, probably because each bird, when the metabolic rate of the birds increased, could allocate more time to foraging due to improved predator detection by many eyes. The vigilance time of Willow Tits decreased with flock size and was determined by the total number of individuals in a flock rather than by the number of Willow Tits in mixed-species flocks of Willow and Coal Tits.     

The significance of clutch overlap in Great Tits Parus major

We studied the effects of manipulation of the size of first broods in the Great Tit Parus major on the size and breeding success of second clutches and its relation to the degree of clutch overlap. The rearing of first brood fledglings always overlapped with the laying of the second clutch and in most cases also with the incubation period of the latter. The degree of clutch overlap depended on the size of the first brood, being less when the first brood was large. Clutch overlap also increased with season. Mechanisms affecting the timing of laying of second clutches are discussed. A large first brood imposed reproductive costs. It affected the size of the second clutch by causing it to be delayed; second clutch size decreases with season. It affected the post-fledging survival of second brood young as, in this population, this decreases with fledging date. The breeding success of second clutches was, however, not affected by the size of the first brood, but instead by the weight of the female when rearing the first brood.     

Experimentally Elevated Plasma Testosterone Levels Do Not Influence Singing Behaviour of Male Blue Tits (Parus caeruleus) During the Early Breeding Season

Sexual selection theory suggests that females might prefer males on the basis of testosterone (T)‐dependent secondary sexual traits such as song. Correlational studies have linked high plasma T‐levels to high diurnal song output. This has been confirmed in experiments where T‐levels were kept high at times when natural T‐levels have decreased. However, surprisingly little is known about the relation between T‐levels during the early breeding season and song. In many passerine birds males sing at a high rate at dawn early in the breeding season, referred to as the dawn chorus. In blue tits (Parus caeruleus), the dawn chorus coincides with the fertile period of the female, whereas diurnal song occurs throughout the breeding season. Previous studies on blue tits showed that characteristics of the dawn chorus correlate with male reproductive success. We experimentally elevated plasma T‐levels in male blue tits during the pre‐fertile and fertile period. Our aim was to test whether increased plasma T‐levels affect dawn song characteristics and increase the amount of diurnal song. Although T‐implants successfully raised circulating T‐levels, we did not find any difference between T‐ and control males in temporal performance measures of dawn song or in diurnal song output. Our results suggest that either there is no direct causal link between song output or quality and individual T‐levels, or experimental manipulations of T‐levels using implants do not permit detection of such effects during the early breeding season. Although we cannot exclude that individual T‐levels are causally linked to other (e.g. structural) song parameters, our results cast doubt on T‐dependence as the mechanisms that enforces honesty on song as a sexually selected trait.     

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

The number of spiders caught by caged Great Tits Parus major in a 10 minute test increased in a sigmoid fashion with ambient temperature between 2 and 13°C. In control tests with immobile prey Calliphora pupae there was no significant effect of temperature. These results indicate that increasing activity of arthropod prey with temperature (Kacelnik 1979b) renders them more vulnerable to predators. We suggest that one reason why small temperate-zone birds such as Great Tits do not forage but sing when they get up in the morning is because low ambient temperatures reduce prey activity and hence the profitability of foraging.     

Extra-pair paternity among Great Tits Parus major following manipulation of male signals

Female Great Tits are known to eavesdrop on the singing behaviour of males. It is unknown, however, whether manipulation of these signals is sufficient to influence extra-pair copulations, or whether such potentially costly reproductive decisions are unaffected by altering short-term signals of condition. Using interactive playbacks, we systematically engaged males in territorial contests in which we could control whether the focal male won or lost the interaction, regardless of the males' true potential. We then determined the levels and patterns of extra-pair paternity among experimental and neighbouring pairs using DNA microsatellite analysis. Extra-pair young were found in equal frequency among the nests of males allowed to win interactions as among those who lost interactions. However, cuckolded males were significantly less variable in allele sizes across the five microsatellite alleles tested than males who were not cuckolded. As measures of genetic variability are increasingly being found to correlate with individual fitness, this may suggest that females are attentive to underlying measures of condition when making extra-pair decisions. Short-term modification of the males' perceived quality may be insufficient to cause females to alter extra-pair decisions.     

The effect of old age on the reproduction of Great Tits Parus major and Blue Tits P. caeruleus

The results from two data sets show that in Great Tits Parus major and Blue Tits P. caeruleus reproduction is influenced by age. In both species, laying dates become earlier while clutch- and brood-size increase between the ages of 1 and 2, but there is no change in nesting success or post-fledging juvenile survival. Great Tits aged 5 or older are 'old' in that laying starts later and nesting success, brood-size and post-fledging juvenile survival decrease. Blue Tits become 'old' 1 year earlier than Great Tits: females aged 4 or older lay later, have a lower nesting success and smaller brood-size, and their young show a decreased post-fledging survival. The effect on laying date, in the Blue Tit, becomes apparent only for females aged 6 and older. It is concluded that ageing in small passerines is to be expected more generally, but that no extrapolations can be made as to the timing of the effect from one species to another.     

The timing of breeding and offspring size in Great Tits Parus major

The relationship between the timing of breeding, offspring weight and offspring recruitment was investigated in two populations of Great Tits Parus major. In two of six seasons a significant negative correlation was found between laying date and fledgling weight, in three seasons the opposite was true and in one season no significant correlation existed between these variables. Offspring recruitment was quantified in five seasons, and late-nesting birds were found to produce significantly fewer recruiting offspring in two of these, the same two seasons when late fledglings had significantly lower weights. No significant correlation existed between the number of recruits and laying date in the three seasons when late fledglings were as heavy as or heavier than early fledglings. The potential detriment to reproductive success of lateness thus was offset when late-nesting parents managed to produce heavy young. Between-year variations in the seasonal pattern of reproductive success has previously been suggested to contribute to the maintenance of variability in the timing of breeding in Great Tits. In this paper we suggest that producing heavy offspring late in the season might be a proximate factor influencing the seasonal patterns of reproductive success. Producing heavy offspring late in the season is probably not a strategy but rather an effect of chance differences between years in the seasonal availability of food or the seasonality of other factors important for the nesting birds.     

Hoarding of individual nuthatches Sitta europaea and march tits Parus palustris

The hoarding behaviour of one pair of nuthatches Sitta europaea L. and of four individual marsh tits Parus palustris L. was studied during autumn and winter in a deciduous grove in central Sweden. Sunflower seeds were offered at a feeding table. AM individuals studied stored seeds intensively throughout the whole study period. The two species showed very different hoarding patterns. The nuthatch pair aggressively defended the area around the feeding table, which was within their territory, from other nuthatches and also seemed to affect the hoarding behaviour of the coexisting marsh tits. Some significant differences were found also between con-specifics in some aspects of hoarding behaviour, which could in some cases be related to sex or dominance. These differences may make hoarding profitable for the individual birds if they also differ in their foraging patterns individually, and so will have a greater probability of finding their own stored items than other individuals. However, the evidence for individual segregation of hoarding patterns is not conclusive.     

Winter survival and breeding success of dominant and subordinate Willow Tits Parus montanus

We studied the effect of winter rank on survival rate and reproductive success in Willow Tits Parus montanus, a resident passerine living in dominance-structured flocks during the nonbreeding season, in 6 years. Winter survival was dependent on both the birds' age and rank. Adults survived better than first-year birds, and within first-year males, dominants survived better than subordinates. In other sex and age classes, rank did not contribute to survival. Although first-year males were in excess among nonbreeders, no connection existed between breeding status and rank. Female rank did not explain the variation in the start of laying, clutch size, number of fledglings or recruit production. We conclude that social status in Willow Tits affects individual fitness mainly through rank-dependent survival. Acquiring a high rank position seems to be most important for first-year birds, especially first-year males.     

Dominance and anti-predator behaviour of Great Tits Parus major: a field study

During the winter of 1981–82 the hierarchical system of free-living Great Tits Parus major that visited a feeder supplied with sunflower seeds was studied in relation to the appearance of a predator. Without a predator, dominant birds were more successful in feeding and had to wait less before feeding. A significant negative correlation was found between dominance and the sequence of initial arrival.
After a Sparrowhawk Accipiter nisus had flown over the feeder, a correlation was found between the birds' dominance and the sequence of their return to the feeder. This field study supports the results of an analogous investigation on anti-predator behaviour and dominance in captive Blue Tits P. caeruleus.     

Laying date of marsh tits Parus palustris in relation to climate change

Increasing evidence suggests that climate change affects bird breeding phenology and other life-history traits of wildlife. This study is based on the mean spring temperatures (February, March, April) and laying dates of first eggs of the marsh tit Parus palustris. We collected data from 1984 to 2004 for the Mokrice area in NW Croatia. Correlation between laying date and mean spring temperatures was significant. The relationship between mean laying date (y) and air temperature (x) can be expressed as y = 44.69 − 2.08x. Results indicate that spring temperatures are a good predictor of timing of laying eggs. Such long-term data could than be used in order to assess the effects on biological systems if human activities influence climate.     

Habitat structure influences the song characteristics within a population of Great Tits Parus major

Capsule: The structure of Great Tit Parus major songs is shaped by the acoustic properties of the habitat within the breeding territory of individuals.

Aim: To test whether the structure of the habitat influences song structure within a population of Great Tits P. major.

Methods: We recorded Great Tit songs from 42 territories on two different days and measured the habitat structure in each territory. We also trapped the males and estimated the breeding density around each territory, so were able to control the analysis by date, breeding density and male characteristics.

Results: Song pause length was positively affected by the ground cover, while the song rate and the minimum frequency were negatively affected by the shrub cover. Male size negatively affected the peak frequency of the songs, whereas the age of the males affected the frequency range; older males sang with a broader bandwidth.

Conclusion: This study suggests that Great Tits are capable of adjusting their vocalizations in each territory, presumably to enhance transmission owing to vocal plasticity.     

Social dominance in free-living Willow Tits Parus montanus: determinants and some implications of hierarchy

Several features of social dominance among Willow Tit Parus montanus winter flocks were examined during a four-winter study. Birds of both sexes were evenly distributed over the 33 flocks studied. In nearly half of the flocks there was an adult pair accompanied by yearlings, but one-third of the flocks consisted of more than two adults with yearlings. Males were found to be dominant over and larger than females. Within a sex, yearlings were usually subordinate to adults. The effect of size on dominance, after controlled for sex and age, remained obscure in our field data. The hierarchical status of an individual was found to rise or at least stay the same in different years, which supports the "hopeful dominants" hypothesis, i.e. birds stay in flocks hoping to achieve a higher status in the future. The ranks of mates correlated highly significantly, implying that high-ranking birds were paired with other high-ranking birds and low-ranking birds with other low-ranking birds. Birds of different age and sex did not show any differences in the proportion of initiated aggressive encounters directed at other individuals. However, males were more aggressive to other males than to females and also tended to behave less aggressively towards their own mates than towards other individuals in the flock. This could be a male strategy to strengthen the pair-bond and to enhance mate protection described earlier in     

青海西宁大山雀的鸣唱模式分析

2012年4~5月在西宁市录制大山雀的鸣声,用Avisoft-SASLab Pro声音分析软件分析其鸣唱结构。已有的录音记录分析表明西宁大山雀个体拥有1~4种鸣唱型,鸣唱短语由1~5个音素构成。西宁大山雀2音素短语的长度低于低海拔地区,具有较快的鸣唱型转换频率。