Long-term consequences of early ontogeny in free-living Great Tits Parus major

Environmental factors during early development may have profound effects on subsequent life-history traits in many bird species. In wild birds, sex-specific effects of early ontogeny on natal dispersal and future reproduction are not well understood. The objective of this work was to determine whether hatching date and pre-fledging mass and condition of free-living Great Tits Parus major have any subsequent effect on individuals’ natal dispersal and reproductive performance at first breeding. Both males and females dispersed longer distances in coniferous than in deciduous forests, while dispersal was condition-dependent only in males (heavier as nestlings dispersed farther). In females, mass and condition at pre-fledging stage correlated significantly with clutch size, but not with subsequent reproductive performance as measured by fledging success or offspring quality. In contrast, heavier males as nestlings had higher future fledging success and heavier offspring in their broods compared with those in worse condition as nestlings. The hatching date of female as well as male parents was the only parental parameter related to the number of eggs hatched at first breeding. These results indicate that pre-fledging mass and condition predict subsequent fitness components in this bird species. We suggest that sex-specific relationships between a disperser’s condition and its selectivity with respect to breeding habitat and subsequent performance need to be considered in future models of life-history evolution.     

Variation of adult Great Tit Parus major body condition and blood parameters in relation to sex, age, year and season

In recent years, an increasing number of studies have focused on the ranges of variation of health related biochemical and haematological parameters in wildlife, but information is still scarce for enzymatic activities which can be extremely important in detecting potential responses to environmental change. In a Great Tit (Parus major) population, we describe the variation in relation to age, sex, season and year of: (1) morphological: body condition index, fat and muscle, (2) haematological: hematocrit, haemoglobin, white blood cell count and heterophil/lymphocyte ratio, and (3) biochemical parameters: plasma protein and activities of plasma cholinesterases (acetylcholinesterase and butyrylcholinesterase) activity and red blood cell glutathione peroxidase. Sex had significant effects on all morphological parameters except fat. Age significantly affected cholinesterase activities, H/L ratio and haemoglobin, and there was a significant interaction between sex and age affecting hematocrit. There were significant interactions of year and season affecting almost all parameters studied—body condition index, fat, protein, acetyl and butyrylcholinesterase activities, glutathione peroxidase activity and haemoglobin. This study indicates that these parameters are largely influenced by year and seasonal effects, besides the individual’s intrinsic variation. Therefore, when evaluating experimental or environmental change effects, appropriate controls should be used.     

Selection for fast and slow exploration affects baseline and stress-induced corticosterone excretion in Great tit nestlings, Parus major

In nestlings, glucocorticoid (GC) secretion has short-term and long-term f itness consequences. For example, short-time elevations trigger begging activity, whereas chronically elevated GC levels impair body condition, growth and cognitive abilities. Despite a growing body of literature on personality traits, the effects of selection for fast and slow exploration on GC secretion have received little attention. We compared baseline and stress-induced hypothalamic–pituitary–adrenal (HPA) axis activity of hand-reared great tit nestlings of lines selected for fast and slow exploration. Nestling droppings were collected under three conditions: control, test (following handling stress, day 14 after hatching) and the following day. The concentrations of excreted immunoreactive corticosterone metabolites (CM) were determined via an enzyme immunoassay. We also observed nestlings' begging behaviour. CM differed significantly between the lines. Nestlings of the fast line excreted lower CM than slow-line birds. In response to handling stress, nestlings excreted significantly higher concentrations of CM than during the control and on the day after handling. Sex and begging activity were not related to CM levels. Under the control condition, but not after handling, males begged significantly more often than females. In both lines, adults excreted significantly less CM compared to nestlings. Both nestlings and adults of the slow line produced higher baseline CM values than fast-line birds. Fast-line nestlings excreted lower baseline CM than nestlings of a wild population not selected for fast or slow exploration. Slow-line nestlings did not. Our results show that selection on the basis of exploratory behaviour affected HPA axis reactivity.     

Breeding success and lutein availability in great tit (Parus major)

The relationship among temporal variation in the availability of carotenoid-rich food, tissue carotenoid levels and breeding success are poorly known. We studied how diet quality and quantity affect the carotenoid profile and fledging success of great tit (Parus major) nestlings along a pollution gradient. We found declining seasonal trend in lutein concentration of caterpillars, which may be the explanation for the declining trend in nestlings' lutein concentration of plasma with season, despite the increase in caterpillar biomass. This may be because the biomass of most lutein-rich caterpillars (autumnal moths) decreased and less lutein-rich caterpillars (sawflies) increased during the breeding season. The temporal difference in occurrence of different caterpillar species means that peak lutein availability does not coincide with peak caterpillar abundance. However the positive association between total larval biomass and the number of great tit fledglings may suggest that fledging success depends more on total caterpillar availability than on lutein concentration of caterpillars.     

Pollination of the Crown ImperialFritillaria imperialis by Great TitsParus major

Visitations of flowers of the Crown Imperial by Great Tits at two different locations in Hessen, Germany, in 1990 and 1993 are described. The observations prove that flowers were visited because of the nectar; most likely pollination occurs during this visits. Similar reports from Europe are discussed. The significance of specific interactions including ecological generalists such as the Great Tit is considered in the context of the phylogenetic reconstruction of the development of co-adaptive syndroms.

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Zusammenfassung Beobachtungen von Kohlmeisen (Parus major) an Blütenständen der Kaiserkrone (Fritillaria imperialis) in Hessen zeigen, daß der Blütenbesuch des Nektars wegen erfolgte und daß dadurch mit größter Wahrscheinlichkeit eine Bestäubung der Pflanzen erreicht wird. Ähnliche Fälle aus Europa werden diskutiert. Die Bedeutung spezifischer Interaktionen unter Beteiligung ökologischer Generalisten wie der Kohlmeise für die Rekonstruktion der phylogenetischen Entstehung co-adaptiver Syndrome wird erörtert.

     

Body mass of female great tits (Parus major) at egg laying

Based on automated weighing of nest-boxes, we found that female great tits (Parus major) usually maintained their body mass during the egg-laying period. A drop in temperature (3°C or more) during laying was followed by a drop in body mass, and female body mass also depended slightly but significantly on mean temperature on the other days. Day to day change in body mass depended negatively on the actual body mass. Moreover, the repeatability of the morning body mass was high (r _I =0.90, n=24). Thus, female body mass seems to be regulated around a female specific, but temperature-dependent, level during laying. The lack of strong correlation between female average body mass and clutch size makes it improbable that body mass at laying plays a leading, proximate role in the control of clutch-size of great tits.     

Breeding patterns of great tits ( Parus major ) in pine forests along the Portuguese west coast

The breeding biology of great tits (Parus major) was studied in two forests of maritime pine (Pinus pinaster) on the west coast of Portugal, 200 km apart: Leiria (north) and Aposti?a (south). These two forests are located in a transition zone between Atlantic climate in the north, and Mediterranean climate in the south. Breeding onset was, on average, in the second and third week of March, which are the earliest records of breeding for this species. The southern population started to breed earlier than the northern one and produced a larger first clutch, 8.3 and 7.4 eggs, respectively. Corresponding to larger clutch sizes, we also found a higher first brood fledgling production in Aposti?a compared to Leiria, 6.1 and 5.4 fledglings, respectively. However, the total number of fledglings produced per pair was higher in Leiria (8.3) than in Aposti?a (7.7), due to higher productivity of second clutches (4.7 and 2.7 fledglings, respectively). Accordingly, the allocation of eggs between successive breeding attempts was more equal in Leiria. Results are discussed in accordance to the different climatic patterns in the two areas. It is suggested that the timing of breeding and different allocation of reproductive investment between successive breeding attempts play an important role in optimizing breeding tactics in this facultative multiple-brooded passerine in different climatic areas.     

Relationship between temperature and the timing of breeding of the Blue Tit (Parus caeruleus) in two Mediterranean oakwoods

Summary Correlations between warmth sum and egg laying in tits (Paridae) were often found but do not prove that there is a direct influence of temperature on egg laying date. Such correlations are also open to criticism because they involve a statistical bias (i. e. the selection of variables). Studies of a Blue Tit population in two close but different habitats in Mediterranean France showed that it is better, at least, to consider a time period with a physiological signification (1 January–10 April). We found that the higher the mean temperature in this time period, the earlier the egg laying commenced. Egg laying dates of the Blue Tit in the two habitats are primarily attributed to habitat-related feeding resources.

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Zusammenfassung Die zahlreich publizierten Korrelationen zwischen Wärmesummen und Beginn der jährlichen Legeperiode bei Meisen (Paridae), bilden keinen Beweis für einen direkten Einfluß der Temperatur auf den Legebeginn. Solche Korrelationnen beruhen außerdem auf statistische fraglichen Auswertungen. Untersuchungen an einer Blaumeisenpopulation (Parus caeruleus) in zwei benachbarten, aber verschiedenen Bruthabitaten im mediterranen Südfrankreich zeigten, daß höchstens ein längerer Zeitabschnitt (1. Januar bis 10. April) mit physiologischer Bedeutung in Betracht zu ziehen ist. Je höher die Durchschnittstemperatur in dieser Periode, um so früher der Legebeginn, der jedoch hauptsächlich durch die zeitlich unterschiedlichen Nahrungsangebote in den beiden untersuchten Habitaten erklärt wird.

     

Calcium effects on life-history traits in a wild population of the great tit (Parus major): analysis of long-term data at several spatial scales

Calcium is an essential micronutrient for birds during egg formation and for skeletal development in nestlings. Habitat level studies suggest that birds breeding in low-calcium areas may be limited in the size or number of eggs they lay and in the quality of their nestlings. However, as birds forage non-randomly and may travel considerable distances to acquire calcium, describing different breeding environments in terms of their calcium availability is problematic. Here we explore the spatial relationships between 300-fold variation in soil calcium and the life-history traits of ca. 6,000 pairs of great tits breeding in a single continuous woodland over 41 years. Controlling for other habitat differences, we found strong positive associations between soil calcium, clutch size and recruitment at spatial scales of over 300 m from each nestbox, suggesting that females may have been travelling inter-territorially to acquire calcium during egg formation. Soil calcium near each nestbox (mean distance = 58 m) was a strong positive predictor of mean fledgling mass, suggesting that local calcium was more important during nestling stages. We found no effect of soil calcium on lay-date or egg mass. This study is the first to provide evidence that small woodland passerines are limited by calcium availability at several different spatial scales. However, experimental work is necessary to test the causality of these spatial patterns.     

Leishmania major: Secreted antigens of Leishmania major promastigotes shift the immune response of the C57BL/6 mice toward Th2 in vitro

BALB/c mice are sensitive to Leishmaniamajor infection, while C57BL/6 mice are resistant and able to mount an effective immune response against the parasite. Since the secreted antigens of L. major suppress the proliferation of BALB/c mice lymphocytes in vitro, we analyzed their effects on the immune system of resistant C57BL/6 mice. Secreted antigens were semi-purified and two fractions with immunosuppressive activity were isolated. 15 μg/ml of fraction could suppress 60% of lymphocyte proliferation and prevent the stimulated lymphocytes entering from G1 phase into the S phase of the cell cycle. These fractions decreased the production of IFN-γ, increased IL-4 level in the lymphocyte culture and down-regulated the nitric oxide production by activated macrophages. These results may suggest that L. major parasite by secreting immunosuppressive factors could down-regulate the immune system of both sensitive and resistant mice for own survival advantage.     

The physiology of hypothermia in the black-capped Chickadee,Parus atricapillus

Summary The shivering, body temperature, and metabolic response to stable and decreasing ambient temperature were measured in winter acclimatized Black-capped Chickadees,Parus atricapillus. Shivering activity, measured by duration and amplitude of bursts, increased curvilinearly from thermoneutral temperatures of 27°C down to 0°C. This parabolic shivering response may be a major component of the curvilinear response of metabolism to decreasing ambient temperature.Birds exposed to 0°C exhibited metabolism 32–45% lower than predicted for a 12-g homeotherm and body temperatures 10°C below the pre-experimental nocturnal body temperature. This hypothermia was not the result of a breakdown in thermoregulation, but was a controlled effort serving to reduce overnight energy expenditure. It is suggested that (1) hypothermia was achieved by decreased shivering by pectoral muscles during exposure to decreasing ambient temperatures, (2) the rate of body temperature decline was moderated by intermittent and reduced bursts during the cooling period, and (3) body temperature was maintained at a particular level during exposure to a stable low ambient temperature by intense bursts lasting one to three minutes.The physiology of hypothermia in chickadees is similar to torpor; however, chickadees did not arouse to a normal diurnal body temperature in the laboratory, and their hypothermia was not induced by inanition or prolonged exposure to cold, as reported for other species capable of torpor.     

Plasma levels of luteinizing hormone and steroid hormones in free-living winter groups of willow tits (Parus montanus)

Plasma levels of LH, DHT, testosterone, and corticosterone were measured for all members in free-living winter flocks of willow tits, Parus montanus. Hormonal data were related to (1) flock size and (2) age/sex differences. The winter flock defends a large winter territory and shows a well-established social hierarchy in which adults consistently dominate first-year birds. One winter group normally consists of four individuals, two adults and two juveniles. In flocks containing four or five members juvenile willow tits had significantly higher corticosterone values than adults. In small-sized groups, containing three members, all individuals had high plasma levels of corticosterone. No other effects of flock size was found. When data were treated on an age/sex basis, i.e., flock size was not considered, juvenile females were found to have significantly higher plasma levels of testosterone than adult birds, and also significantly higher levels of DHT than juvenile males and adult females. Also, juvenile willow tits had significantly higher plasma levels of corticosterone than adult birds.     

Reproductive investment and parasite susceptibility in the Great Tit

1. Reproduction and parasite defence are assumed to be costly activities for hosts, and therefore trade-offs might exist between reproduction and parasite defence.
2. Brood sizes were manipulated in a population of Great Tits ( Parus major L.) to assess trade-offs between reproduction and parasite defence. Blood samples were taken from males and females during the late nestling phase, and parasite prevalence was compared among parents raising enlarged, reduced and control broods.
3. A higher prevalence of protozoan blood parasites dominated by Haemoproteus majoris was found among parents with enlarged broods, as compared with parents with control and reduced broods, respectively. Brood size manipulation did not affect parasite prevalence between the sexes or between age classes differently.
4. Mean parasite intensity (number of parasites per microscope field) among adult birds only infected with H. majoris was higher for parents with experimentally enlarged broods than controls and reduced broods, respectively.
5. These results support the hypothesis of a trade-off between parasite defence and reproduction.     

Immune Activation Reduces Sperm Quality in the Great Tit

Mounting an immune response against pathogens incurs costs to organisms by its effects on important life-history traits, such as reproductive investment and survival. As shown recently, immune activation produces large amounts of reactive species and is suggested to induce oxidative stress. Sperm are highly susceptible to oxidative stress, which can negatively impact sperm function and ultimately male fertilizing efficiency. Here we address the question as to whether mounting an immune response affects sperm quality through the damaging effects of oxidative stress. It has been demonstrated recently in birds that carotenoid-based ornaments can be reliable signals of a male''s ability to protect sperm from oxidative damage. In a full-factorial design, we immune-challenged great tit males while simultaneously increasing their vitamin E availability, and assessed the effect on sperm quality and oxidative damage. We conducted this experiment in a natural population and tested the males'' response to the experimental treatment in relation to their carotenoid-based breast coloration, a condition-dependent trait. Immune activation induced a steeper decline in sperm swimming velocity, thus highlighting the potential costs of an induced immune response on sperm competitive ability and fertilizing efficiency. We found sperm oxidative damage to be negatively correlated with sperm swimming velocity. However, blood resistance to a free-radical attack (a measure of somatic antioxidant capacity) as well as plasma and sperm levels of oxidative damage (lipid peroxidation) remained unaffected, thus suggesting that the observed effect did not arise through oxidative stress. Towards the end of their breeding cycle, swimming velocity of sperm of more intensely colored males was higher, which has important implications for the evolution of mate choice and multiple mating in females because females may accrue both direct and indirect benefits by mating with males having better quality sperm.     

Genetic variation in the timing of reproduction in the Great Tit

Summary About 40% of the population variation in the initiation dates of first clutches within years is genetically determined. The onset of laying, which is determined by the female, is not detectably influenced by spatial heterogeneity of the study area.There is a variable selection favoring early, middle, or late laying in some years. Over the study period as a whole there is a slight net selection for laying relatively late.The implications for a potential rapid evolutionary change are discussed. The conclusion is reached that the population mean might change with rates of up to one week per five generations, which is approximately a decade.     

Competition and egg-weight in the Great Tit Parus major

The mean weight of eggs in clutches of the Great Tit Parus major varies markedly between clutches. Eggs are lighter in years of high density of breeding pairs than in years of low density, but egg weight is also inversely correlated with the density of breeding Blue Tits Parus caeruleus .