Geographic variation in the occurrence of song types in Nuthatch Sitta europaea populations

The frequency of occurrence of song types of Nuthatches Sitta europaea was examined in nine study areas in northern Belgium. Birds from different areas did not differ consistently in the use of five distinct song types, and similarity in the occurrence of song types was not related to geographic distance, except that one song type, "Ud", was almost wholly absent from four areas in the northeast of the investigated area. In the remaining areas, the frequency of occurrence of this song type varied from 10% to 20%. This presence/absence pattern appears to be stable between years. I suggest that the birds from the four areas lacking "Ud" were descended from a formerly small and highly isolated population near Antwerp, where the song may have been lost through a founder effect. Birds in areas with and without "Ud" did not differ in their response level to playback of this song, except that those in areas without "Ud" were incapable of song matching.     

Breeding behaviour of Nuthatch Sitta europaea in relation to natural hole attributes in a primeval forest

Capsule Nuthatches used holes with strong walls, typically in live trees with entrances reduced by plastering, and ‘oversized’ interiors filled with bark flakes.

Aims To describe patterns of nest-site utilization by Nuthatches in primeval conditions, to examine the influence of various hole attributes on nesting success and to consider the adaptive value of nest-site choice.

Methods Observations of birds living in undisturbed conditions in a strictly protected part of the Bia?owie?a National Park (Poland) during 27 breeding seasons coupled with measurements of hole attributes and observations of nests' fate.

Results Tree species used for breeding differed among habitats. Holes were on average 14.0 m above the ground, in trees with girth at breast height 206 cm; both parameters varied strongly among tree species. They were situated mainly in tree trunks (76%), in living trees (89%), in conical knotholes (51%); woodpecker-made holes constituted 32%. Nuthatches bred in very large (mean bottom area: 325 cm²) holes, the preferred tree species (Maple Acer platanoides, Ash Fraxinus excelsior) had larger holes than other tree species. Nuthatches reduced entrances by ‘plastering’ to a mean size of 2.9 × 3.3 cm. They made the holes substantially shallower by filling them with bark flakes (mean depth to nest level: 10 cm), eggs were laid in depressions among flakes, far from the entrance (mean distance: 21 cm), their ‘nests’ occupied only a fraction of the hole area. Broods in holes with smaller entrances were the most successful. Eggs and small young were covered with bark during the absence of the female. Larger nestlings, when endangered, moved to the rear wall of the hole, where they stayed tightly pressed. These behaviour patterns reduced the risk of predation.

Conclusion The features of holes used by Nuthatches (combination of strong walls, small entrances and large bottoms with copious filling) are probably an evolutionary solution to the need to evade predators while keeping contents of the nest dry.     

普通鳾的巢位选择和繁殖成功巢特征

普通对巢位具有选择性,利用树种共7种,利用率不同,利用树洞类型有两种,啄洞利用率高,结洞低。洞口朝向在西至西偏北45°方向的树洞利用率最低,其它方向差异不大。洞口处树的直径、洞口纵径、洞内径、洞深和洞周围10m范围,树的密度5个巢位变量在利用和未利用树洞之间差异极显著(P<001),洞口横径,洞口处树干与垂直方向夹角和洞口方向90°角10m范围树的密度差异显著(P<005),其余变量差异不显著(P>005)。23巢平均窝卵数778±095,孵化率8994%,出飞率9627%。30个巢中成功巢和失败巢的11个巢位特征比较发现,洞高和洞口方向90°角10m范围内树的密度差异极显著,洞口纵径和洞口横径差异显著,其余变量差异不显著。     

Bigger male Eurasian nuthatches (Sitta europaea) behave more aggressively in playback-simulated territorial intrusion

Journal of Ethology - In animals, personality (or temperament) is associated with alternative response patterns in reaction to a potential stressor or challenging situation. Aggressiveness is one...     

Habitat fragmentation reduces disperser success in juvenile nuthatches Sitta europaea: evidence from patterns of territory establishment

We studied establishment in summer territories by first-year nuthatches Sitta europaea both in a large forest and in a set of small and isolated forest fragments (2 yr in each area) In the large forest, vacant territories were rapidly taken up by newly formed pairs of juveniles In the fragments settlers arrived at a slower rate more of them remained unpaired, and more territories remained vacant at the end of the dispersal period Furthermore, territories were taken up in a highly predictable order related to territory quality in the large forest, but not so in the fragments We suggest that dispersal is more costly in a highly fragmented habitat reducing the number of settlers at the population level, and reducing opportunities for pair formation and habitat selection at the individual level     

Selection of mature and old stands by Corsican Nuthatch Sitta whiteheadi in harvested forests

In harvested forests, the bird community is largely determined by stand structure, which itself is determined by forestry practices. This study aimed to identify habitat variables determining the presence of Corsican Nuthatch Sitta whiteheadi – a threatened island endemic – in harvested Corsican Pine Pinus nigra laricio woods, with the aim of mitigating the impact of timber harvest on the bird. Comparison of occupied and unoccupied plots showed that this bird is found mostly in pure Corsican Pine stands, and is absent when more than 50% of trees are not this species. Nests were built in decaying pine snags between 20 and 100 cm diameter at breast height (dbh), but birds avoided stands with live pines < 70 cm dbh, and selected stands with pines > 80 cm dbh. Conservation of Corsican Nuthatch therefore depends on maintaining harvest rotations of more than 200 years, reducing the size of felling coupes in clear‐cutting systems or, preferably, practising selective cutting, maintaining a sufficient density of old trees and snags, and checking the encroachment of other tree species into Corsican Pine stands.     

Phylogenetic relationships of Eurasian Nuthatches (Sitta europaea Linnaeus, 1758) from the Alborz and Zagros Mountains,Iran

The Eurasian Nuthatch (Sitta europaea Linnaeus, 1758) is a resident bird in the Alborz and Zagros deciduous forests. We investigated the phylogenetic relationships and the taxonomic position of the Eurasian Nuthatch among other separated lineages of Eurasia with the help of blood samples collected from 19 individuals belonging to four populations in the Eastern and Western Alborz, as well as in the Northern and Southern Zagros forests. Genetic variation was then analysed using complete ND2 gene sequence (1041?bp) and phylogenetic analysis was done using Bayesian and maximum likelihood inference. Additionally, a median-joining algorithm was used to reveal the relationships among haplotypes. The results of the phylogenetic and haplo-type network analyses indicated that Eurasian Nuthatch haplotypes from the Alborz and Zagros Mountains form lineages distinct from the Asian, Caucasian and European haplotypes. Furthermore, an analysis of molecular variance (AMOVA) detected significant (P<0.001) genetic structure among the lineages. The Asian, European, Caucasian and Alborz lineages diverged from one another by an uncorrected genetic distance ranging from 0.029 to 0.039, while the Zagros lineage showed a slightly lower genetic divergence from the Caucasian lineage (0.006), but it did not share any haplotype with the Caucasian lineage. Thus, we suggest considering five Conservation Significant Units (CSU) for the Eurasian Nuthatches as the result of used dataset.     

Age- and sex-related differences in dominance and foraging behaviour of nuthatches Sitta europaea

Nuthatches collecting sunflower seeds from feeders were observed. In summer, but not in autumn, adults collected more seeds per visit than juveniles. From summer to autumn, juveniles increased both the number of seeds collected per unit time and the total number taken per visit. This was probably due to an increase in both experience and ability to handle seeds, possibly associated with beak growth. Males were dominant over females, and adults over juveniles of the same sex. Dominance relations were important in determining the length of visits; males made longer visits. Males also took more seeds per visit. However, females obtained more seeds per unit time, probably to avoid being supplanted by males.     

Individual contributions to territory defence in a cooperative breeder: weighing up the benefits and costs

While investment in territory defence is expected to be influenced by its benefits, the additional role that costs may play is rarely considered. Here, we quantify both benefits and costs of repelling prospecting males in cooperative meerkats, and demonstrate that both are required to explain the substantial variation in individual contributions to the defence observed. Males benefit more from repelling prospectors than females, as males may lose dominance and be expelled during intrusions. Accordingly, males invest the most in repelling prospectors. We also show that males experience an associated cost in the form of reduced weight gain and, as such, heavier males contribute more to chasing prospectors. Finally, we show evidence of a cost not restricted to individuals engaged in chasing: both males and females reduce their contributions to feeding dependent pups when prospectors are present, resulting in a reduction in pup weight gain in this context. Males appear to adjust their contributions to chasing in light of this cost, chasing at lower rates when their group contains dependent young. Our findings support the view that investment in cooperative behaviours can be attributed to benefits and costs, and highlight the additional importance of considering trade-offs in investment between cooperative behaviours.     

Shifts to earlier selfing in sympatry may reduce costs of pollinator sharing

Coexisting plant congeners often experience strong competition for resources. Competition for pollinators can result in direct fitness costs via reduced seed set or indirect costs via heterospecific pollen transfer (HPT), causing subsequent gamete loss and unfit hybrid offspring production. Autonomous selfing may alleviate these costs, but to preempt HPT, selfing should occur early, before opportunities for HPT occur (i.e., “preemptive selfing hypothesis”). We evaluated conditions for this hypothesis in Collinsia sister species, C. linearis and C. rattanii. In field studies, we found virtually identical flowering times and pollinator sharing between congeners in sympatric populations. Compared to allopatric populations, sympatric C. linearis populations enjoyed higher pollinator visitation rates, whereas visitation to C. rattanii did not differ in sympatry. Importantly, the risk of HPT to each species in sympatry was strongly asymmetrical; interspecies visits comprised 40% of all flower‐to‐flower visits involving C. rattanii compared to just 4% involving C. linearis. Additionally, our greenhouse experiment demonstrated a strong cost of hybridization when C. rattanii was the pollen donor. Together, these results suggest that C. rattanii pays the greatest cost of pollinator sharing. Matching predictions of the preemptive selfing hypothesis, C. rattanii exhibit significantly earlier selfing in sympatric relative to allopatric populations.     

Selective neutrality of mitochondrial ND2 sequences, phylogeography and species limits in Sitta europaea

Variation and geographic differentiation in mitochondrial DNA (mtDNA) was studied in the widespread and phenotypically variable Eurasian nuthatch (Sitta europaea). To assess whether sequences were evolving in a selectively neutral fashion, we used McDonald–Kreitman [Nature 351 (1991) 652] tests and a tree-based method, which suggested that although ND2 sequences are affected by natural selection against slightly deleterious alleles, the effects do not compromise phylogeographic inferences. Three phylogenetic species-level clades of nuthatches were discovered, corresponding to the Caucasus, southern Europe, and northern Europe plus Asia. Unimodal mismatch distributions within each clade suggest that populations have undergone recent growth. A westward range expansion was inferred from the geographic pattern in nucleotide diversity. Although samples were insufficient, it is possible that nuthatches in England and Japan are recently differentiated. Two specimens of the subspecies S. e. arctica formed a sister group to all other S. europaea, differing by ca. 10% uncorrected sequence divergence, pointing the need for additional study of this phenotypically distinct taxon. As with other species, mtDNA data support major phenotypic distinctions, but not subspecies.     

A prudent hoarder: effects of long-term hoarding in the European nuthatch, Sitta europaea

Although hoarding has been studied intensively for many decades,few studies have attempted to measure its actual fitness consequences.To fill this gap, we used ptilochronology, the growth of replacementfeathers as a measure of nutritional status, and thus a reflectionof starvation risk, of individual European nuthatches (Sittaeuropaea) during winter. We found that nuthatches are long-termhoarders, retrieving stored food up to at least 98 days afterstoring it. Long-term hoarding enhanced the nutritional statusof individual birds significantly because those individualsexperimentally given an opportunity to store seeds during autumnregrew plucked rectrices faster and larger than did controlbirds. Nuthatches used their stored seeds prudently by adjustingthe amounts they ate to meet their requirements, as determinedby ambient temperatures. Nuthatches refrained from using storedfood during periods of relatively benign conditions so theycould use the food during periods of more severe conditions.     

Nuthatches (Sitta europaea: Aves) in forest fragments: demography of a patchy population

Breeding density, local survival and summer recruitment of nuthatches were evaluated in a population scattered over many small (1–30 ha) forest fragments, and compared with study plots inside larger forests. Since most young birds settle outside the fragment in which they were born this population corresponds to the “patchy population” concept implying that patterns in abundance may be better explained by processes at the population level than by metapopulation processes. Mean breeding density was c. 50% lower in fragments and decreased with regional isolation (distance from larger forests) but not with local isolation (distance to nearby fragments). Local survival of adults and established (i.e. territorial) 1st-year birds was not related to forest size or isolation. However, fewer young birds settled in summer in the fragments compared with a large forest. This difference probably reflects high mortality during the sensitive dispersal phase. Moreover, the observed number of recruits and their estimated survival was insufficient to maintain the breeding population, suggesting significant net immigration from larger forests. This “rescue effect” explains why densities are affected by regional, but not local isolation. Received: 14 December 1998 / Accepted: 1 March 1999     

Impact of shrub canopies on understorey vegetation in western Eurasian tundra

Question: How does the composition and species richness of understorey vegetation associate with changing abundance of deciduous shrub canopies? What are the species‐specific associations between shrubs and understorey plants? Location: Tundra habitats along an over 1000‐km long range, spanning from NW Fennoscandia to the Yamal Peninsula in northwest Russia. Methods: The data from 758 vegetation sample plots from 12 sites comprised cover estimates of all plant species, including bryophytes and lichens, and canopy height of deciduous shrubs. The relationships between shrub volume and cover of plant groups and species richness of vegetation were investigated. In addition, species‐specific associations between understorey species and shrub volume were analysed. Results: Shrub abundance was shown to be associated with the composition of understorey vegetation, and the association patterns were consistent across the study sites. Increased forb cover was positively associated with shrub volume, whereas bryophyte, lichen, dwarf shrub and graminoid cover decreased in association with increasing volume of deciduous shrubs. The total species richness of vegetation declined with increasing shrub volume. Conclusions: The results suggest that an increase of shrubs – due to climatic warming or a decrease in grazing pressure – is likely to have strong effects on plant–plant interactions and lead to a decrease in the diversity of understorey vegetation.     

The day after: effects of vocal interactions on territory defence in nightingales

1. Models on territory acquisition and tenure predict that territorial animals benefit by adjusting territorial defence behaviour to previous challenges they had experienced within the socially complex environment of communication networks. 2. Here, we addressed such issues of social cognition by investigating persisting effects of vocal contests on territory defence behaviour in nightingales Luscinia megarhynchos (Brehm). 3. Using interactive playback during nocturnal song of subjects, a rival was simulated to countersing either aggressively (by song overlapping) or moderately (by song alternating) from outside the subjects' territory. Thereby, the time-specific singing strategy provided an experimentally controlled source of information on the motivation of an unfamiliar rival. 4. Expecting that nightingales integrate information with time, the same rival was simulated to return as a moderately singing intruder on the following morning. 5. The results show that the vigour with which male nightingales responded to the simulated intrusion of an opponent during the day depended on the nature of the nocturnal vocal interaction experienced several hours before. 6. Males that had received the song overlapping playback the preceding night approached the simulated intruder more quickly and closer and sang more songs near the loudspeaker than did males that had received a song alternating playback. 7. This adjustment of territory defence strategies depending on information from prior signalling experience suggests that integrating information with time plays an important part in territory defence by affecting a male's decision making in a communication network.     

Foraging behaviour of Nuthatches(Sitta europaea) in relation to the presence of mates and mixed flocks

Summary Nuthatches (Sitta europaea) usually forage in pairs outside the breeding season. I investigated whether foraging site selection in winter (tree species, height, substrate size) differed between sexes and whether this difference was related to the presence of mixed-species flocks. Foraging sites of pair members foraging together were highly correlated. In the rare cases when each used different tree species, males foraged significantly more often on the preferred oak trees than females. Males foraged significantly lower than females in some territories, but not in others. The reasons for this significant variation between pairs remains unexplained. Males also foraged lower than females in the company of mixed flocks. These differences are probably better explained as avoidance of the dominant male by the subordinate female, rather than specialization in resource use to avoid competition.

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Nahrungssuche beim Kleiber (Sitta europaea) im Paarverbund und in gemischten Schwärmen

Zusammenfassung Außerhalb der Brutzeit fouragieren Kleiber gewöhnlich in Paaren. Ich untersuchte, ob sich die Geschlechter in der Wahl des winterlichen Nahrungsortes (Baumart, Höhe, Astdicke) unterscheiden und ob solche Unterschiede durch die Anwesenheit von gemischten Schwärmen beeinflußt ist. Die Ortswahl der gemeinschaftlich auf Nahrungssuche gehenden Paarpartner war hoch korreliert. In den seltenen Fällen, in denen sich die Partner an verschiedenen Bäumen aufhielten, fanden sich die Männchen signifikant mehr an den der Art bevorzugten Eichen als die Weibchen. In einigen Revieren fouragierten die Männchen an signifikant niedrigeren Standorten als die Weibchen, doch war dies nicht in allen Revieren der Fall. Die Ursachen für diese Unterschiede sind nicht bekannt. Auch in gemischten Schwärmen erfolgte die Nahrungssuche der Männchen niedriger als die der Weibchen. Möglicherweise vermeiden die Weibchen so die Konkurrenz durch die dominanten Männchen.

     

Differential effects of moving versus stationary territorial intruders on territory defence in a songbird

1.  In territorial contests, not only acoustic or other signals, but also the movements of a territorial intruder are likely to influence the response of a resident.
2.  We tested this movement hypothesis by simulating moving vs. stationary intruders into the territories of winter wrens Troglodytes troglodytes , using the same non-interactive song playbacks in both treatments.
3.  Male winter wrens showed a different long-term singing reaction in response to a moving than to a stationary intruder.
4.  One day after experiencing an intruder that was switching between three locations, residents started to sing earlier before sunrise, and they sang more and longer songs at dawn than before the intrusion.
5.  Residents receiving the same playback from one location only reacted by starting to sing later relative to sunrise, and by singing fewer and shorter songs than before the intrusion.
6.  We could not discriminate between the treatments when examining the short-term singing reactions during and immediately after the playbacks. However, our results clearly demonstrate an effect of the spatial behaviour of territorial intruders on the long-term territory defence of residents at dawn, about 24 h after an intrusion.
7.  We argue that spatial behaviour of territorial intruders should be an integral part of the study of animal territory defence behaviour. Investigating long-term changes in territory defence at dawn is a sensitive tool for discriminating between different types of intruders.     

Seasonal acclimatization of metabolism in Eurasian tree sparrows (Passer montanus)

Acclimatization to winter conditions is an essential prerequisite for survival of small passerines of the northern temperate zone. Changes in photoperiod, ambient temperature and food availability trigger seasonal acclimatization in physiology and behavior of many birds. In the present study, seasonal adjustments in several physiological, hormonal, and biochemical markers were examined in wild-captured Eurasian tree sparrows (Passer montanus) from the Heilongjiang Province in China. In winter sparrows had higher body mass and basal metabolic rate (BMR). Consistently, the dry mass of liver, heart, gizzard, small intestine, large intestine and total digestive tract were higher in winter than in that in summer. The contents of mitochondrial protein in liver, and state-4 respiration and cytochrome c oxidase (COX) activity in liver and muscle increased significantly in winter. Circulating level of serum triiodothyronine (T₃) was significantly higher in winter than in summer. Together, these data suggest that tree sparrows mainly coped with cold by enhancing thermogenic capacities through increased organ masses and heightened activity of respiratory enzymes activities. The results support the view that prominent winter increases in BMR are manifestations of winter acclimatization in tree sparrows and that seasonal variation in metabolism in sparrows is similar to that in other small temperate-wintering birds.