Population Of Tits Research Articles

Age-dependent phenological plasticity in a wild bird.

Life-history traits are often plastic in response to environmental factors such as temperature or precipitation, and they also vary with age in many species. Trait variation during the lifetime could thus be partly driven by age-dependent plasticity in these traits. We study whether plasticity of a phenological trait-the egg-laying date-with respect to spring temperature, varies with age, and explore whether this variation relates to changes in breeding success throughout the life cycle. We use data from a four-decade long-term monitoring of a wild population of blue tits in Corsica, to estimate age-dependent plasticity of reproductive phenology and annual reproductive success. We show that both laying date plasticity and annual reproductive success vary with age: young and old females are less plastic, and fledge fewer offspring, than middle-age females. Furthermore, in contrast to young and prime-age females, in old females fledging success does not depend on laying date. Phenological plasticity is a major mechanism for coping with rapid environmental variation. Our results suggest that understanding its role in adaptation to climate change and population persistence requires integrating the age structure of the population.

Analysis of within-individual variation in extrapair paternity in blue tits (Cyanistes caeruleus) shows low repeatability and little effect of changes in neighborhood.

Many studies investigated variation in the frequency of extrapair paternity (EPP) among individuals. However, our understanding of within-individual variation in EPP remains limited. Here, we comprehensively investigate variation in EPP at the within-individual level in a population of blue tits (Cyanistes caeruleus). Our study is based on parentage data comprising >10 000 genotyped offspring across 11 breeding seasons. First, we examined the repeatability of the occurrence of EPP, the number of extrapair offspring, the number of extrapair partners, and the occurrence of paternity loss using data from males and females that bred in multiple years. Second, we tested whether within-individual changes in EPP between breeding seasons relate to between-year changes in the local social environment. Repeatabilities were generally low but significant for the occurrence and number of extrapair young in females and for whether a male sired extrapair young or not. We found no evidence that the presence of the former social partner or changes in the proportion of familiar individuals or in phenotypic traits of the neighbors influenced changes in levels of EPP in females. However, in adult males, a decrease in the average body size of male neighbors was associated with higher extrapair siring success. If confirmed, this result suggests that the competitive ability of a male relative to its neighbors influences his extrapair mating success. We suggest that alternative hypotheses, including the idea that within-individual changes in EPP are due to “chance events” rather than changes in an individual’s social breeding environment, deserve more consideration.

Seasonal rainfall in subtropical montane cloud forests drives demographic fluctuations in a Green-backed Tit population

Abstract Montane birds are vulnerable to climate change. However, the mechanisms by which weather drives demographic processes in montane birds have seldom been investigated. We conducted a long-term study (2009–2019) on the Green-backed Tit (Parus monticolus), an insectivorous passerine, in the montane cloud forest of subtropical Taiwan. We explored the effects of weather variability on the productivity and survival of adult Green-backed Tits. Nest survival was negatively associated with seasonal rainfall during the breeding season (April–July) and was lower in early clutches than in late clutches. Higher typhoon-induced precipitation during the postbreeding period (July–September) was related to reduced adult survival, but neither summer temperature nor winter weather conditions were found to be related to adult bird survival. We developed a stochastic simulation model for Green-backed Tit population dynamics based on empirical data. We compared the simulated time-series and observed population growth rates (λ) and found that 80% (8/10 yr) of the observed λ fell within the 5th and 95th percentiles of the simulated data over the 10-yr period. Moreover, the simulated average (± standard deviation) of the geometric mean of λ over 10 yr (1.05 ± 0.07) was close to that observed from 2009 to 2019 (0.99), which provided confidence that the model effectively simulated the population growth rate of the Green-backed Tit. We conducted a sensitivity analysis for λ and found that juvenile and adult survival influenced by typhoon-induced rainfall were the greatest contributors to the variance in the growth rate of the Green-backed Tit population. With the onset of intensified seasonal precipitation associated with global warming, the population growth and density of Green-backed Tits will decline substantially. Our results suggest that under scenarios of high emissions of greenhouse gas, this local population of Green-backed Tits will not persist in the near future.

Negative effects of individual heterozygosity on reproductive success in a wild bird population.

The evolutionary consequences of individual genetic diversity are frequently studied by assessing heterozygosity-fitness correlations (HFCs). The prevalence of positive and negative HFCs and the predominance of general versus local effects in wild populations are far from understood, partly because comprehensive studies testing for both inbreeding and outbreeding depression are lacking. We studied a genetically diverse population of blue tits in southern Germany using a genome-wide set of 87 microsatellites to investigate the relationship between proxies of reproductive success and measures of multilocus and single-locus individual heterozygosity (MLH and SLH). We used complimentary measures of MLH and partitioned markers into functional categories according to their position in the blue tit genome. HFCs based on MLH were consistently negative for functional loci, whereas correlations were rather inconsistent for loci found in nonfunctional areas of the genome. Clutch size was the only reproductive variable showing a general effect. We found evidence for local effects for three measures of reproductive success: arrival date at the breeding site, the probability of breeding at the study site and male reproductive success. For these, we observed consistent, and relatively strong, negative effects at one functional locus. Remarkably, this marker had a similar effect in another blue tit population from Austria (~400km to the east). We suggest that a genetic local effect on timing of arrival might be responsible for most negative HFCs detected, with carry-over effects on other reproductive traits. This effect could reflect individual differences in the distance between overwintering areas and breeding sites.

Fight or flight: Geographic variation in antipredator defenses by cinereous tits

In the face of death from predation, parent birds have to choose between prioritizing current versus future reproduction. Previous studies have shown that when exposed to predation risk, birds breeding in the tropics prioritize their own safety, whereas birds breeding at high latitudes prioritize the safety of future generations. However, this phenomenon has rarely been investigated among populations within a single bird species. Here, we studied the anti-predation behavior of female birds in response to a human observer of four cinereous tit (Parus cinereus) populations during their incubation period across different latitudes in China. When confronted with nest predation risk induced by the presence of a human, the probability of escape by cinereous tits decreased with increasing latitude, that is, the proportion of female birds that escaped from the nest was significantly larger in southern than in northern populations. For female birds that did not leave the nest, the proportion of individuals who produced a hissing call for nest defense was significantly lower in the southern than in the northern populations. In addition, nest defense behaviours were unrelated to nest predation rates, and clutch size in the southern cinereous tit populations was significantly smaller than that in the northern population, it was, therefore, likely that nest defense behaviours were related to clutch size. The present study confirms within a single species that under predation risk, female birds in the tropics prioritize future over current reproduction, while the birds breeding at high latitudes do the opposite.

Nest Predation in the African Blue Tit, Cyanistes teneriffae (Aves, Paridae), Using Nest-Boxes and Artificial Nests

Predation on breeding blue tit populations in north-eastern Algeria has been studied in nest boxes during a five years fieldwork (2003-2007) in cork oak forests. Nest boxes were placed each year in Brabtia plain forest in El Kala National Park. Results have shown that mean nest predation rate is 51.74%. Six patterns of nest predation have been described and five predators are probably involved: Common Genet, Great Spotted Woodpecker, Ocellated Lizard, Ants and Rodents. Genet is the major predator on tit nests. Mean predation rates on egg and nestling stages are similar. Artificial nests and natural nests had similar predation rates. Major predators on artificial nests were lizards and Rodents.

Wilding of a post-industrial site provides a habitat refuge for an endangered woodland songbird, the British Willow Tit Poecile montanus kleinschmidti

ABSTRACT Capsule Post-industrial sites that have become wilded by colonizing vegetation can represent important habitat refuges for Willow Tits Poecile montanus, which occupy large territories in early-successional wet woodland and scrub. Aims To quantify Willow Tit population density and territory characteristics on a habitat mosaic of wetland, grassland and woodland/scrub, which has developed on a 596 ha area of former coal mining activities in northwest England. Methods Field surveys located all 35–37 nests per year during 2017–2019. Territories were estimated using Thiessen polygons around nest sites. Remote sensing data (land cover mapping and lidar) characterized woody vegetation height and coverage across the site and within territories. Changes in coverage between 1990 and 2015 were assessed to estimate the age of woody vegetation. The relationship between territory size and woodland was tested to see if birds secure a similar area and volume of woody vegetation in each territory. Results Mean breeding density was 7.3 pairs/km2 (excluding 103 ha of ponds/lakes). Estimated territories averaged 13.7 ha, or 6.9 ha in wooded habitat only. The woodland and scrub were a maximum of 25–30 years old and had a mean height of 3.7 m. Larger territories contained a greater coverage and volume of wooded habitat. The site held 1.3% of the national and global population of the British subspecies of Willow Tit. Conclusion Willow Tits occur at low density and require large areas of habitat. Wilded post-industrial sites appear to be important for Willow Tit conservation in Britain, but may require ongoing management to maintain the early-successional woodland and scrub associated with new wetlands in former mining areas. Such sites may have a broader conservation value for a range of species.

Demographic history and genomics of local adaptation in blue tit populations.

Understanding the genomic processes underlying local adaptation is a central aim of modern evolutionary biology. This task requires identifying footprints of local selection but also estimating spatio‐temporal variations in population demography and variations in recombination rate and in diversity along the genome. Here, we investigated these parameters in blue tit populations inhabiting deciduous versus evergreen forests, and insular versus mainland areas, in the context of a previously described strong phenotypic differentiation. Neighboring population pairs of deciduous and evergreen habitats were weakly genetically differentiated (F ST = 0.003 on average), nevertheless with a statistically significant effect of habitat type on the overall genetic structure. This low differentiation was consistent with the strong and long‐lasting gene flow between populations inferred by demographic modeling. In turn, insular and mainland populations were moderately differentiated (F ST = 0.08 on average), in line with the inference of moderate ancestral migration, followed by isolation since the end of the last glaciation. Effective population sizes were large, yet smaller on the island than on the mainland. Weak and nonparallel footprints of divergent selection between deciduous and evergreen populations were consistent with their high connectivity and the probable polygenic nature of local adaptation in these habitats. In turn, stronger footprints of divergent selection were identified between long isolated insular versus mainland birds and were more often found in regions of low recombination, as expected from theory. Lastly, we identified a genomic inversion on the mainland, spanning 2.8 Mb. These results provide insights into the demographic history and genetic architecture of local adaptation in blue tit populations at multiple geographic scales.

Does offspring sex ratio differ between urban and forest populations of great tits (Parus major)?

Since male and female offspring may have different costs and benefits, parents may use sex ratio adjustment to increase their own fitness under different environmental conditions. Urban habitats provide poorer conditions for nestling development in many birds. Therefore, we investigated whether great tits (Parus major) produce different brood sex ratios in urban and natural habitats. We determined the sex of nestlings of 126 broods in two urban and two forest sites between 2012 and 2014 by molecular sexing. We found that brood sex ratio did not differ significantly between urban and forest habitats either at egg-laying or near fledging. Male offspring were larger than females in both habitats. This latter result suggests that male offspring may be more costly to raise than females, yet our findings suggest that urban great tits do not produce more daughters despite the unfavourable breeding conditions. This raises the possibility that other aspects of urban life, such as better post-fledging survival, might favour males and thereby compensate for the extra energetic costs of producing male offspring.

It takes two: Heritable male effects on reproductive timing but not clutch size in a wild bird population.

Within-population variation in the traits underpinning reproductive output has long been of central interest to biologists. Since they are strongly linked to lifetime reproductive success, these traits are expected to be subject to strong selection and, if heritable, to evolve. Despite the formation of durable pair bonds in many animal taxa, reproductive traits are often regarded as female-specific, and estimates of quantitative genetic variation seldom consider a potential role for heritable male effects. Yet reliable estimates of such social genetic effects are important since they influence the amount of heritable variation available to selection. Based on a 52-year study of a nestbox-breeding great tit (Parus major) population, we apply "extended" bivariate animal models in which the heritable effects of both sexes are modeled to assess the extent to which males contribute to heritable variation in seasonal reproductive timing (egg laying date) and clutch size, while accommodating the covariance between the two traits. Our analyses show that reproductive timing is a jointly expressed trait in this species, with (positively covarying) heritable variation for laydate being expressed in both members of a breeding pair, such that the total heritable variance is 50% larger than estimated by traditional models. This result was robust to explicit consideration of a potential male-biased environmental confound arising through sexually dimorphic dispersal. In contrast to laydate, males' contribution to heritable variation in clutch size was limited. Our study thus highlights the contrasting extent of social determination for two major components of annual reproductive success, and emphasizes the need to consider the social context of what are often considered individual-level traits.

Novel sources of (co)variation in nestling begging behavior and hunger at different biological levels of analysis

Abstract Biological hypotheses predicting patterns of offspring begging typically concern the covariance with hunger and/or development at specific hierarchical levels. For example, hunger drives within-individual patterns of begging, but begging also drives food intake among individuals within broods, and begging and food intake can covary positively or negatively among genotypes or broods. Testing biological phenomena that occur at multiple levels, therefore, requires the partitioning of covariance between traits of interest to ensure that each level-specific relationship is appropriately assessed. We performed a partial cross-fostering study on a wild population of great tits (Parus major), then used multivariate mixed models to partition variation and covariation in nestling begging effort and two metrics of nestling hunger within versus among individual nestlings and broods. At the within-individual level, we found that nestlings begged more intensely when hungrier (positive correlation between begging and hunger). However, among individuals, nestlings that were fed more frequently also begged more intensely on average (negative correlation between begging and hunger). Variation in nestling mass did not give rise to the negative correlation between begging and hunger among nestlings, but we did find that lighter nestlings begged more intensely than their heavier biological siblings, suggesting that this effect may be driven by a genetic component linked to offspring size. Our study illustrates how patterns of covariance can differ across biological levels of analysis and addresses biological mechanisms that could produce these previously obscured patterns.

On the presence of Willow Tit <em>Poecile montanus</em> in the Central Apennines

[Since the mid Fifties data have been published stating the presence of a Willow Tit population on the Central Apennines. The Authors, after controlling all available information and comparing them with the morphological and eco-ethological features of the species, hypothesize that all Willow Tit recorded observations relate instead to Marsh Tit, concluding that no Willow Tit populations were ever recorded in the area]. [Article in Italian]

Multiple factors affect discrimination learning performance, but not between-individual variation, in wild mixed-species flocks of birds.

Cognition arguably drives most behaviours in animals, but whether and why individuals in the wild vary consistently in their cognitive performance is scarcely known, especially under mixed-species scenarios. One reason for this is that quantifying the relative importance of individual, contextual, ecological and social factors remains a major challenge. We examined how many of these factors, and sources of bias, affected participation and performance, in an initial discrimination learning experiment and two reversal learning experiments during self-administered trials in a population of great tits and blue tits. Individuals were randomly allocated to different rewarding feeders within an array. Participation was high and only weakly affected by age and species. In the initial learning experiment, great tits learned faster than blue tits. Great tits also showed greater consistency in performance across two reversal learning experiments. Individuals assigned to the feeders on the edge of the array learned faster. More errors were made on feeders neighbouring the rewarded feeder and on feeders that had been rewarded in the previous experiment. Our estimates of learning consistency were unaffected by multiple factors, suggesting that, even though there was some influence of these factors on performance, we obtained a robust measure of discrimination learning in the wild.

Song overlapping, noise, and territorial aggression in great tits

Abstract Communication often happens in noisy environments where interference from the ambient noise and other signalers may reduce the effectiveness of signals which may lead to more conflict between interacting individuals. Signalers may also evolve behaviors to interfere with signals of opponents, for example, by temporally overlapping them with their own, such as the song overlapping behavior that is seen in some songbirds during aggressive interactions. Song overlapping has been proposed to be a signal of aggressive intent, but few studies directly examined the association between song overlapping and aggressive behaviors of the sender. In the present paper, we examined whether song overlapping and ambient noise are associated positively with aggressive behaviors. We carried out simulated territorial intrusions in a population of great tits (Parus major) living in an urban–rural gradient to assess signaling and aggressive behaviors. Song overlapping was associated negatively with aggressive behaviors males displayed against a simulated intruder. This result is inconsistent with the hypothesis that song overlapping is an aggressive signal in this species. Ambient noise levels were associated positively with aggressive behaviors but did not correlate with song rate, song duration, or song overlapping. Great tits in noisy urban habitats may display higher levels of aggressive behaviors due to either interference of noise in aggressive communication or another indirect effect of noise.

Longitudinally monitored lifetime changes in blood heavy metal concentrations and their health effects in urban birds

Urban heavy metal pollution can impair the health of humans and other organisms inhabiting cities. While birds are suggested as one of the appropriate bioindicators for essential and non-essential trace element monitoring, the process of particular elements' accumulation in blood and its possible adverse health effects during ageing of individuals remain unexplored. We have investigated lifetime changes in blood lead (Pb), cadmium (Cd), arsenic (As) and zinc (Zn) concentrations and searched for links to health-related traits in sub-urban free-living great tit (Parus major) population monitored over a long period of time. The blood As concentrations were under the limit of detection in most samples. The blood Pb levels showed a non-linear relationship to individuals age, where the highest Pb concentrations were measured in nestlings and in a very small group of highly senescent birds (over 7 years old), while no clear trend was observed for the majority of the adult age stages. No age-related patterns were found for blood Cd or Zn concentrations. The positive relationship between date of capture and blood Cd and Zn levels may reflect seasonal changes in diet composition. We did not reveal any anaemia-like conditions (decreased total erythrocyte count or increased immature erythrocyte count) in relation to blood heavy metal concentrations in the investigated birds. Total leukocyte counts, heterophil/lymphocyte (H/L) ratio and total heterophil and lymphocyte counts increased with increasing Pb, Cd and Zn concentrations in blood. This study demonstrates the suitability of avian blood for actual heavy metal spatial and temporal biomonitoring even in situations when the precise age of the individuals remains unknown.

Timing of arrival in the breeding area is repeatable and affects reproductive success in a non-migratory population of blue tits.

Events in one part of the annual cycle often affect the performance (and subsequently fitness) of individuals later in the season (carry-over effects). An important aspect of this relates to the timing of activities. For example, many studies on migratory birds have shown that relatively late-spring arrival in the breeding area reduces both the likelihood of getting a mate or territory and reproductive success. In contrast, relatively little is known about the movements of individuals in non-migratory populations during the non-breeding season. Few studies have investigated the timing of arrival at the breeding area in such species, possibly due to the assumption that most individuals remain in the area during the non-breeding season. In this study, we used 4years of data from a transponder-based automated recording system set up in a non-migratory population of blue tits Cyanistes caeruleus to describe individual variation in arrival at the breeding site. We investigated whether this variation can be explained by individual characteristics (sex, body size or status), and we assessed its effect on aspects of reproductive success in the subsequent breeding season. We found substantial variation in arrival date and demonstrate that this trait is individual-specific (repeatable). Females arrived later than males, but the arrival dates of social pair members were more similar than expected by chance, which suggests that individuals may mate assortatively depending on their arrival in the breeding area. Arrival predicted both whether an individual would end up breeding that season and several aspects of its breeding success. Our study suggests that individuals of non-migratory species leave the breeding area during the non-breeding season. Hence, it may be useful to consider variation in the scale of movements between breeding and non-breeding sites, rather than using a simple dichotomy between 'resident' and 'migratory' species. We conclude that the timing of pre-breeding events, in particular arrival date, may be an overlooked, but important, fitness-relevant trait in non-migratory species.

Extreme temperature drop alters hatching delay, reproductive success, and physiological condition in great tits

It has been suggested that extreme weather events may be treated as natural experiments that may unravel the mechanisms by which birds adjust their phenology and breeding parameters to environmental variability. In 2017, a sudden and heavy drop of temperatures for several days affected many European bird populations. This event occurred during the laying–early incubation period in the great tit (Parus major) population in central Poland, causing a large delay in hatching and had sustained reproductive consequences. This cold snap occurring once breeding activity had already started in 2017 was followed by the warm and invariable breeding season of 2018. This natural experiment had an essential influence on great tit reproductive parameters. We found a significant difference in hatching date, number of fledglings, hatching success, and fledging success between 2017 and 2018. In 2017, there were about two fledglings per nest fewer than in 2018. Fledging success was positively associated with hatching delay in 2017, while the relation was negative in 2018. Hatching success differed significantly between both years, being higher in 2018. Mean level of hemoglobin (used as index of body, physiological condition) in the blood of nestling great tits was higher in 2017 than in 2018. We argue that the moment of hatching may be (at least in some years) more tightly related to the moment of maximum food demand of tit nestlings than the traditionally used laying date. Also in extreme years, phenotypic plasticity of hatching delays may be insufficient to adjust the timing of breeding to the upcoming extreme weather events. Further examining its limits may be an important goal for future research.

Differences in the breeding performance of great tits Parus major between a forest and an urban area: a long term study on first clutches

The great tit Parus major inhabits various types of forests, yet it prefers deciduous forests. In the urbanized areas it is one of the commonest bird species, even where only isolated trees are present, which seems to be a relatively recent phenomenon. This paper presents results of a long-term study (2002–2015) of variation in reproductive performance (number of hatchlings, hatching success, number of fledglings, fledging success, breeding success and nest failure rate) in first clutches of two great tit populations nesting in two contrasting habitats: a mature deciduous forest and an urban parkland, in central Poland. This study shows a clear and sustained spatial pattern of variation where the forest population of great tits produced more hatchlings and fledglings per successful nests than the urban park site population. Breeding success and fledging success demonstrate a similar but slightly less obvious pattern, with higher values for the forest site than the urban parkland area occurring consistently in the vast majority of years. Also hatching success was generally slightly higher in the forest than in the urban park but did not show such a clear spatial pattern. Only the nest failure rate was higher in the forest than in the urban parkland. We suggest that caterpillar richness in the forest compared to the urban parkland is one of the key drivers of the observed differences in the breeding performance between the study habitats. We also found positive correlations between fledgling numbers and caterpillar abundance and between fledgling numbers and mean May temperatures in the forest, whereas neither breeding nor fledging success showed such correlations. In the urban parkland, fledgling numbers as well as fledging and breeding successes were positively correlated with mean May temperatures. The between-population variation we found probably reflects a more general difference between urban and forest populations of tits.

Consequences of hatching deviations for breeding success: a long-term study on blue tits Cyanistes caeruleus

The causes and consequences of variation in the incubation regimes of oviparous animals remain unclear, despite having important fitness consequences. Avian incubation regimes can be shortened by parents initiating incubation prior to clutch completion or prolonged when there are gaps in the laying sequence. Here, we begin by quantifying variation in the incubation regimes of three populations of blue tits Cyanistes caeruleus from the UK and Poland before examining the consequences of such variation for their hatching and fledging success. We then investigate the mechanism causing such variation by exploring the impact of local weather conditions on incubation regimes. The difference between the expected and actual hatching dates of clutches was termed the “hatching deviation” and this showed considerable variation. Hatching deviation was negatively related to local temperature and clutch size. Hatching deviation affected hatching success and hatching deviation, temperature, wind speed and clutch size affected fledging success. Deviating from the expected laying and incubation regime caused lowered reproductive success. The most successful birds were those that were able to lay one egg per day and begin incubation upon clutch completion.

Subtle differences in breeding performance between Great Tits Parus major and Afrocanarian Blue Tits Cyanistes teneriffae in the peripheral zone of the species geographic ranges in NE Algeria

Because of the geological history of North Africa, populations of Great Tits Parus major existing in this region experienced less geographical isolation from populations of continental Europe than populations of Afrocanarian Blue Tits Cyanistes teneriffae. As a result, North African Great Tits are more ephemeral in their distribution and habitat choice as well as less ecologically generalist than their European continental conspecifics. By contrast, the Afrocanarian Blue Tit forms a separate species which is closely related to the Blue Tit Cyanistes caeruleus of Europe, including Mediterranean islands. Afrocanarian Blue Tits are a versatile generalist species. Here we compare some aspects of the breeding ecology of Great Tits and Afrocanarian Blue Tits in a highland area of the Algerian Aures Mountains facing the Sahara in the south. For both the tit species this area constitutes peripheral part of their distributions. We found that in two breeding seasons Great Tits started laying eggs on similar average dates as Afrocanarian Blue Tits, whereas in one year they preceded the latter species. Great Tits laid larger clutches than Afrocanarian Blue Tits. Fledging success was similar between the two species, with Great Tits prospering slightly better in the year when broods of Great Tits were also less infested by blow flies than broods of Afrocanarian Blue Tits. The subtle differences we found between the breeding ecology of Great Tits and Afrocanarian Blue Tits seem to be consistent with Snow’s idea that these species in North Africa differ in a degree of adaptation to local conditions.