Cannibalism in common kestrel (Falco tinnunculus)

acta ethologica - We report two separate observations of adult male common kestrel (Falco tinnunculus) killing and feeding upon second-year (SY) conspecifics in Israel. On 22 January 2022, while...     

Daytime variation in T-cell-mediated immunity of Eurasian kestrel Falco tinnunculus nestlings

Host-parasite interactions are central in evolutionary and behavioural ecology. In the last few years, skin injections of the mitogen Phytohaemagglutinin (PHA) have become one of the most important and widely used in-vivo assays of immune function in birds. However, there are no studies of the circadian variation suggesting that care should be taken interpreting results when using this technique. This 3-year study assessed PHA responses as a function of daylight time in 310 Eurasian kestrel Falco tinnunculus nestlings at 24 days of age in Central Spain. I found that T-cell-mediated immunity was positively related to nestling mass and varied among years. Controlling for these variables, I also found that T-cell-mediated immunity decreased with the hour of sampling, and that this pattern was consistent between years. In addition, I found that at the end of the day only, T-cell-mediated immunity decreased with brood size. Parasites seem not to be behind this pattern, but I suggest that the cumulative effect of sibling competition during the day might explain the decrease of cellular immunity with the hour of sampling. Thus, I strongly recommend that future studies of cellular immunity should control for this potential source of variation when nestling self-maintenance is evaluated by the PHA-induced skin-swelling response.     

Environmental and genetic components of oxidative stress in wild kestrel nestlings (Falco tinnunculus)

In this study, we estimated the environmental and genetic components of two variables related to avian oxidative stress using wild nestlings of the Eurasian kestrel (Falco tinnunculus). The study was carried out during two breeding seasons. In the first season, we assessed the between- and within-nest resemblance in serum reactive oxygen metabolites (ROMs) and total serum antioxidant barrier (OXY). In the second season, we carried out a cross-fostering experiment to determine the importance of environmental and genetic factors on ROMs and OXY. The 23.5% of ROMs variance was explained by the nest of origin, indicating a main genetic component. In contrast, the 52.8% of OXY variance was explained by the nest of rearing, indicating that this variable was more influenced by environmental components. These findings suggest that variations in ROMs and OXY could reflect, respectively, the expression of different genetic polymorphisms and differences in dietary uptake of antioxidants.     

Correlates of oxidative stress in wild kestrel nestlings (Falco tinnunculus)

The fitness of an organism can be affected by conditions experienced during early development. In light of the impact that oxidative stress can have on the health and ageing of a bird species, this study evaluated factors accounting for the variation in oxidative stress levels in nestlings of the Eurasian kestrel (Falco tinnunculus) by measuring the serum concentration of reactive oxygen metabolites and the serum antioxidant barrier against hypochlorite-induced oxidation. The ratio between these two variables was considered as an index of oxidative stress, with higher values meaning higher oxidative damage. Six-chick broods showed the highest level of oxidative stress, while no effect of sex was found. Age showed an inverse relationship with the oxidants and the levels of oxidative stress, with younger birds having higher levels. Hatching date, body condition, body mass and carotenoid concentration did not show any relationship with oxidants, antioxidants or degree of oxidative stress. These findings suggest that intrabrood sibling competition could play a role in determining oxidative stress, and that in carnivorous birds other antioxidant molecules could be more important than carotenoids to reduce oxidative stress.     

Isolation and characterization of polymorphic microsatellite markers in lesser kestrel (Falco naumanni) and cross-amplification in common kestrel (Falco tinnunculus)

Lesser kestrel, Falco naumanni, is a colonial and migratory species breeding in part of the Mediterranean Basin and part of central Asia and north-east of China and Mongolia. This species is catalogued in IUCN red list category as vulnerable. Twenty microsatellite loci were selected from libraries enriched in AC or AG tandem repeats and specific PCR were devised from their flanking sequences. Most microsatellites (14) were found polymorphic among 30 individuals of F. naumanni representing 20 reproduction areas of the species in the region of Extremadura, Spain. Polymorphisms were detected by size variation of the amplified loci, which allele number and observed heterozygosity ranged from 3 to 20 and from 0.300 to 0.933, respectively. Cross-species amplification showed that 13 of selected loci were also found polymorphic in common kestrel species (Falco tinnunculus). Novel polymorphic microsatellites will serve to conservation studies in lesser kestrel.     

Energetic limitation of avian parental effort: Field experiments in the kestrel (Falco tinnunculus)

We studied the limiting factors for brood size in the kestrel, Falco tinnunculus, by measuring parental effort in natural broods of different size and parental response to manipulation of food satiation of the brood. Parental effort was quantified as total daily time spent in flight, and total daily energy expenditure, from all-day observations. During nestling care males with different natural brood sizes (4 to 7 chicks), spent an average of 4.75 h · d^?1 in flight independent of brood size, and expended an average total daily energy of 382 kJ · d^?1. Due to a higher flight-hunting yield (mammal-prey caught per hour hunting), males with larger natural broods were able to provision their broods with the same amount of food (mainly Microtus arvalis) per chick (62.6 g · d^?1), with the same effort as males with smaller broods. This provisioning rate was close to the mean feeding rate of hand-raised chicks in the laboratory, that were fed ad libitum, (66.8 g · d^?1 · chick^?1). Our food deprivation experiments revealed that male kestrels strongly respond to food shortage in the nest. In the older nestling phase males on average increased their daily rate of food delivery to the nest as a response to experimental food deprivation by almost three times to 646.4 g · d^?1, by increasing their flight activity level from 4.46 to 8.41 h · d^?1. This increased energy expenditure was sustained, for as long as eleven days, by increasing the metabolizable energy intake up to what is presumed to be the maximum rate. Even under considerable experimental food stress (chicks not being satiated due to continuous removal of delivered food by the observers) about half of the available daylight time remained unused for foraging. We conclude 1) that the mean daily energy expenditure of males during nestling care — to which clutch size is apparently initially adjusted — is well below the maximum they are able to sustain and 2) that the energy expenditure they can sustain under extremely high nestling demand is not set by the available time for foraging or the available energy in the environment. Thus the birds normally operate well below their presumed maximum, and only during food shortage, e.g., as caused by our experiments, do they increase activity up to this maximum. Therefore we conclude that the kestrels have costs other than energy expenditure, such as parental survival, that are involved in the increased “cost” of parental effort. We discuss possible generalisations about existing energetic limitations during parental care in altricial birds. From published estimates of daily energy expenditure during parental care (DEE_par) in 30 different bird species we derived the equation: DEE_par = 14.26 kg^0.65 Watt. This relationship differs significantly in slope (T = 2.49; p > 0.02) from the allometric equation for the maximum rate of energy assimilation (DME_max) as provided by Kirkwood (1983): DME_max = 19.82 kg^0.72 Watt. In smaller species (ca. 25 g) DEE_par about equals DME_max, while in the larger species (ca. 10 kg) DEE_par represents only about 60% of the predicted DME_max. This suggests that limitations in parental effort are more frequently set by the maximum sustainable energy intake in the smaller species than in larger species. Our allometric equations for DEE_par suggests that the relation between BMR, estimated using the equations of Aschoff and Pohl (1970), and the observed parental energy expenditure, is such that on average bird parents work at a daily level somewhere between 3 and 4 times BMR.     

Skin carotenoid concentration correlates with male hunting skill and territory quality in the kestrel Falco tinnunculus

In the context of sexual selection carotenoid based signals are candidates for indicator traits: they have to be taken up in the diet by animals, they can indicate the ability of the bearer to accumulate a limited resource, and they help in maintaining the health status. We investigated the yellow-orange colouration of the tarsi of the kestrel Falco tinnunculus in relation to sex, diet and to different aspects of male reproductive behaviour. The colouration of the tarsi (estimated as hue) was more intense in males than in females. Among males, the tarsi hue was associated with the intake of invertebrates; this was true also if the population diet was based mainly on voles. Carotenoid based colouration was positively associated with the number of vertebrate preys delivered to the nest per time unit and with territory quality (calculated on the basis of home-range size, habitat extension and prey availability). These results are consistent with predictions derived from good-parent models of sexual selection, suggesting that in the common kestrel carotenoid based colouration is important as an indicator of male quality.     

Innate and learned aspects of vole urine UV-reflectance use in the hunting behaviour of the common kestrel Falco tinnunculus

Some birds are known to use the UV reflectance in their feeding strategy. Knowing that the common kestrel Falco tinnunculus is able to recognise vole trails by perceiving the UV reflectance of their scent marks, this study was designed to investigate whether the use of scent marks in the UV range has an innate component, or if it is only acquired with experience. We tested the preference of 44 experienced adult and 49 naïve juvenile common kestrels in four types of arenas: (1) scent-marked and covered with a UV transmitting filter (UV+SC), (2) scent-marked and covered with a UV blocking filter (UV-SC), (3) sprinkled with water and covered with a UV transmitting filter (UV+W), and (4) sprinkled with water and covered with a UV blocking filter (UV-W). We assessed the birds' preference by counting the number of visual scans and visits to each arena. The distribution of scans differed from random in both adults and juveniles. The birds scanned the UV+SC arena more often than the others. Since naïve individuals showed the same preference as experienced ones, we hypothesised that the association between vole scent UV reflectance and vole presence has an innate component in the common kestrel. Nevertheless, adults differed from juveniles because they perceived the scented arenas from the water sprinkled ones, in fact, adults scanned the UV-SC arena more frequently than both UV+W and UV-W arenas. This result suggests that the ability of detecting UV cues has a learned component.     

A comparative study on the histological structure of the spleen in the ostrich (Struthio camelus), the kestrel (Falco tinnunculus) and the osprey (Pandion haliaetus)

The spleen structurally and functionally belongs to the hematopoietic organs and is also an important component of the reticuloendothelial system, which is known to play a major role in host defense. The histological structure of the spleen was investigated in the ostrich, a non-flying bird, the kestrel, a raptor, and the osprey, a fish-eating bird of prey (fish eagle). For this purpose, Mallory's modified triple stain, methyl green-pyronin and silver stain were used. Germinal centers were not present in the spleen of the osprey. In the spleen of the kestrel, penicillar arterioles and the surrounding lymphoid tissue were markedly dense. Compared to the other two birds, the red and white pulps were clearly distinguishable in the spleen of the ostrich.     

上海郊区冬季红隼行为时间分配

2003年11月~2004年2月采用随机个体、连续取样的方式,在上海郊区获取了越冬112只次红隼(Falco tinnunculus)123.33 h的行为数据,对红隼的时间行为分配模式进行了研究与分析。结果表明,冬季红隼白天活动时间大部分用于栖停(44.45%),其次为捕食(18.83%)、停落(12.17%)、飞行(9.98%)、滑翔(8.11%)、悬停(3.46%)、梳羽(1.70%)、戏耍和交互(1.32%)。栖停在早中晚占有较高的比例,而捕食在上午和下午分别具有一个高峰时段。红隼在1 d中具有两个活动高峰分别在上午(8∶00~10∶00)和下午(13∶00~15∶00)。通过对行为发生时间的相关性分析,发现活动高峰主要是由捕食行为及相关的飞行、悬停等行为组成。     

Intraspecific allometry of basal metabolic rate: relations with body size, temperature, composition, and circadian phase in the kestrel, Falco tinnunculus

The relationship between body size and basal metabolic rate (BMR) in homeotherms has been treated in the literature primarily by comparison between species of mammals or birds. This paper focuses on the intraindividual changes in BMR when body mass (W) varies with different maintenance regimens. BMR varied in individual kestrels in proportion to W1.67, which is considerably steeper than the mass exponents for homomorphic change (0.667; Heusner, 1984) for interspecific comparison among all birds (0.677) or raptors (0.678), for interindividual comparison of kestrels on ad libitum maintenance regimens (0.786), and for mass proportionality (1.00). The circadian range of telemetered core temperature also varied more strongly with intraindividual than with interspecific (Aschoff, 1981a) variation in mass. This was due to reduced nocturnal core temperature at low-maintenance regimens, which was, however, insufficient to account for the excessive reduction in BMR. kidney lean mass at Carcass analysis of eight birds sacrificed revealed a disproportionate reduction in heart and kidney lean mass at low-maintenance regimens. We surmise that variation in BMR primarily reflects variation in these metabolically highly active tissues. This may account for positive correlations found between heart, kidney, and BMR residuals relative to interspecific allometric prediction, and between alpha and rho residuals, as expected on the basis of the constant excess of BMR during alpha above BMR during rho (Aschoff & Pohl, 1970a).     

Population genetic structure of the European ground squirrel in the Czech Republic

The European ground squirrel (Spermophilus citellus) is considered an endangered species with declining numbers throughout Europe, most pronounced at the western margin of its distribution area. Being extinct in Germany and Poland, the western margin of its distribution is in the Czech Republic. Here, landscape fragmentation has restricted the ground squirrels into few and very isolated localities where local extinctions still occur. In the present study we analysed European ground squirrels from six Czech and one Slovak localities using five microsatellite loci as genetic marker. The results show a strong genetic differentiation among the investigated populations (mean value of F _ST = 0.16) and high levels of inbreeding (values of F _IS ranged from 0.34 to 0.90). High level of inbreeding is generally considered to affect the viability of each population, which could lead to extinction. One of the most important factors is the lack of migration due to the large distances between the populations and the presence of migration barriers. Based on the results obtained we recommend a few suggestions for a conservation management of this species.     

Population genetic structure of the noxious weed Amaranthus retroflexus in Central Europe

Genetic variation was assessed in a range of populations of Amaranthus retroflexus using isoenzyme analysis. Population genetic diversity was measured by evaluating patterns of variation at six putatively neutral isoenzyme loci (comprising 24 putative alleles) within and among 20 populations of A. retroflexus collected in different habitats: ruderal habitats, cereal fields and hop gardens. Amaranthus retroflexus is a noxious weed of North American origin that infests various crops. Overall, A. retroflexus displayed moderate levels of genetic diversity in comparison with other herbaceous plants. The percentage of polymorphic loci was 50.0%, with mean values of 2.01, 0.142 and 0.227 for the average number of alleles per polymorphic locus (A), observed heterozygosity (H_o) and expected heterozygosity (H_e), respectively. A discrepancy between observed and expected heterozygosity and significant differences from H-W expectation indicate that there is an excess of homozygotes in many populations. As a result, there is strong evidence of inbreeding within populations (F_IS = 0.382) and significant population differentiation (F_ST = 0.270). Even though the species is partly autogamous, inbreeding does not lead to strong inbreeding depression resulting from self-pollination, as inbreeding has no effect on the success of the species in today's countryside. Moreover, allele frequencies detected in agricultural habitats (i.e., cereal fields and hop gardens) differed from those detected in populations collected from ruderal habitats, which is probably caused by systematic application of herbicides in agricultural ecosystems.     

Breeding dispersal of Eurasian kestrels Falco tinnunculus under temporally fluctuating food abundance

Costs and benefits of dispersal can vary in space and time, depending on environmental factors and individual state. Plastic, condition‐dependent dispersal strategies, in which individuals rely on external cues such as food abundance to adjust their dispersal distances, are therefore expected to evolve in temporally fluctuating environments. We examined factors affecting breeding dispersal distances in Eurasian kestrels Falco tinnunculus subsisting on multi‐annually and cyclically fluctuating voles as their main food. We attempted to avoid traditional bias in dispersal studies by having large study areas and by taking detection probabilities into account. We observed 320 dispersal events of male and 215 events of female kestrels from our study areas in western Finland during 24 yr. After correcting for distance‐specific detection probability, the estimates of mean dispersal distances increased two‐fold being still clearly higher for females than males. Vole abundance in the spring of settlement was more important in determining average dispersal distances than vole abundance in the previous autumn. At the population level (cross‐sectional model), both males and females dispersed longer distances when the spring abundance of their main food (voles) was low compared to when it was abundant, as predicted by the food depletion hypothesis. At the individual level (longitudinal model), only females responded to the food situation by dispersing more when food abundance was low in the spring of settlement. Females also dispersed longer when vole abundance in the previous autumn had been high. Individual males did not respond to vole abundance, which implies that the population level response in males might have been caused by long‐distance dispersers, which breed in the study area only in good vole years. Our results show that the dispersal distances of kestrels at northern latitudes depend both on individual properties (gender, age, and possibly individual tendency to disperse) and environmental conditions (temporal variation in main food abundance).     

Population genetic structure in European populations of Spiranthes romanzoffiana set in the context of other genetic studies on orchids

Spiranthes romanzoffiana Cham. is restricted in Europe to the British Isles, where it is recognised as a conservation priority species due to frequent extirpation of populations along with no evidence of seed set; vegetative reproduction has been invoked as the sole means of perpetuation and dispersal. To investigate the reproductive ecology of this species, 17 populations have been sampled for chloroplast microsatellites and amplified fragment length polymorphisms (AFLPs). These markers revealed a previously unsuspected genetic-geographic split in the species, which correlates with differences in patterns of within-population variation. Northern populations were fixed for one chloroplast haplotype but showed high levels of AFLP genotypic diversity consistent with sexual reproduction (proportion of genotypes distinguishable, PD = 0.98). More southerly populations showed fixed differences from the northern populations in their chloroplast haplotype and for 10 AFLP markers. They harboured only 12 unique multilocus genotypes among 113 individuals from six populations (PD = 0.11). These genotypes differed mostly by single bands, and none by more than 4/138 loci, with identical multilocus genotypes occurring in widely separated populations. This uniformity in southern populations is consistent with agamospermous or autogamous reproduction, and/or an extreme population bottleneck. Finally, the observed patterns of population differentiation in S. romanzoffiana are compared with other studies of orchids, revealing a wide range of values that belie recent contrasting published generalisations that claim that orchids show either higher, or lower, levels of population differentiation than other plant families.     

Nest Defence Behaviour of the Eurasian Kestrel (Falco tinnunculus) Against Human Predators

Man has become the main predator of many animal species. Because the characteristics of humans are quite distinct with respect to other terrestrial predators, the cost and benefits of defence behaviour may also differ. In this paper, we study the factors affecting nest defence behaviour of the Eurasian Kestrel ( Falco tinnunculus canariensis ) against a potential human predator throughout the reproductive cycle, as well as the balance of cost and benefits of this behaviour. The study population inhabits the island of Tenerife, and the nests are located on cliffs. The intensity of the defensive behaviour was unrelated to the frequency of human visits, prey abundance (Orthoptera, Coleoptera, lizards, birds and rodents), laying date, or number of offspring in the nest. Both males and females increased their defensive behaviour as the nesting period advanced, particularly when the chicks were older than 15 days. Moreover, the intensity of the defensive behaviour, especially of males, decreased when nests were more inaccessible. Although nest defence behaviour against humans appeared to be similar to those against other predators, the benefits are not clear because the probability of nest robbing was greater for these more aggressive pairs.     

Turnover, age and sex ratios of kestrels (Falco tinnunculus) in south Scotland

This paper examines the composition and turnover of a population of European kestrels Falco tinnunculus L. in the Southern Uplands of Scotland. Turnover was generally high, with most birds staying in the area for only one summer or winter. The rate at which birds arrived or left was highest in autumn and spring, and was independent of population size. During winter, breeding males were more likely to stay on their territories than females, and males that did so were more likely to retain their partners the following year. Breeding success was associated with a greater likelihood of return the following year, except in first-year females which were unlikely to return anyway. The sex ratio was biased toward males in winter, especially in poor vole years when there were also few first-year birds present. The study confirmed the high rate of turnover reported elsewhere in small raptors, and further indicated that the composition and turnover of the population were related to food supply and seasonal patterns of migration.