The importance of key marginal habitat features for birds in farmland: an assessment of habitat preferences of Red-backed Shrikes Lanius collurio in the Italian Alps

Capsule Key marginal habitat features maintain their importance even when they occur at very low density.

Aims To assess the importance for breeding birds of key habitat elements, such as isolated shrubs, hedgerows and untilled vegetation patches.

Methods We investigated the habitat preferences of Red-backed Shrikes Lanius collurio in an agricultural environment where key habitat elements have been dramatically reduced. Based upon data from territorial maps, a fine-scale model of habitat preference was developed and the results of three different analytical approaches (binary logistic regression, multimodel inference and hierarchical partitioning) were compared.

Results The occurrence of Red-backed Shrikes was positively influenced by the extent of non-grazed/mown grassland, isolated bushes and hedgerows, and negatively influenced by woodland cover. The model highlighted the importance of bushes/hedgerows despite their very scarce occurrence in the study areas (overall, average cover only 7.94%). Breeding densities were rather low, but mean densities were slightly higher in pasture zones in which bushes/hedgerows availability was higher than elsewhere.

Conclusion These results confirm the crucial importance of these key marginal elements even in depauperated farmland landscapes. Maintaining and increasing their availability is a key management option for the encouragement of breeding Red-backed Shrikes, and potentially for other species which are also declining in these farmland habitats.     

Habitat preferences of Red-backed Shrikes Lanius collurio and Barred Warblers Sylvia nisoria breeding sympatrically in a wetland/farmland mosaic

Capsule: The Red-backed Shrike Lanius collurio and the Barred Warbler Sylvia nisoria had similar habitat preferences and their territories often overlapped. However, we found that Red-backed Shrikes were more flexible in habitat choice whilst Barred Warblers had more specific requirements.

Aim: We aimed to analyse and compare distribution and habitat preferences of Red-backed Shrikes and Barred Warblers breeding sympatrically in semi-natural landscape in a wetland/farmland mosaic.

Methods: We examined habitat availability and use by the two species within their breeding territories to identify differences in habitat selection.

Results: Territories of both species were similar in habitat composition and used levees, bushes, fallow areas and single trees. However, the spatial characteristics of the territories differed between species. Red-backed Shrikes used a wider range of sizes and shapes of habitat patches, whilst Barred Warblers preferred a more complex landscape structure and a higher diversity of habitat types. We also found that areas of 71% of Barred Warbler and 34% of Red-backed Shrike territories overlapped.

Conclusion: Whilst both species showed similar habitat choices, they appeared to differ significantly in terms of landscape structure: Red-backed Shrikes were more flexible and less selective than Barred Warblers in their habitat choice.     

Seasonal change in Red-backed Shrike Lanius collurio territory quality - the role of nest predation

This paper examines the relationships between territory preference, reproductive performance and nest predation in a Red-backed Shrike Lanius collurio population breeding in rapidly changing farmland. Territory preference was measured by (a) the order of laying dates in territories within years and (b) territory occupation frequency over a five-year period. Seven environmental variables were tested but only the density of Sloe (Blackthorn) Prunus spinosa in territories was correlated positively with territory occupation frequency. Within years, Red-backed Shrikes started to breed earlier in territories with more Sloe, but reproductive performance was not related consistently to territory differences. A high proportion of Sloe-rich territories was vacant each year. Thus, the observed negative association between settlement order and amount of Sloe may reflect a seasonal change in habitat preference. Early breeders prefer Sloe-rich territories whereas late birds prefer Sloe-poor territories. Supporting evidence is that the proportion of occupied territories that was Sloe-rich was higher for early than for average or late first breeding attempts. Moreover, in contrast to early in the season, the probability of a replacement clutch following nest failure was not associated with the amount of Sloe, but increased with increasing densities of Juniper Juniperus communis. Late in the nesting season, pairs breeding in Sloe-rich territories suffered higher nest predation than those breeding in Sloe-poor territories. In early nesting attempts, however, the relationship was reversed. Nest predation is probably an important selective agent on habitat selection since it was the principal factor explaining variation in the numbers of fledglings produced among territories. Thus, the Red-backed Shrike may shift territorial preferences adaptively as the season progresses to match within-season changes in predation pressure in different types of territories.     

The influence of territory characteristics and food supply on the breeding performance of the Red-backed Shrike (<Emphasis Type="Italic">Lanius collurio</Emphasis>) in an extensively farmed region of eastern Poland

The breeding performance of the Red-backed Shrike (Lanius collurio) in relation to the territory characteristics was investigated. The study was conducted in an area of high agricultural land use, characterised by small field size, a more mosaic habitat and low use of mineral fertilisers in comparison to Western European countries. The influence of habitat structure and composition in the territory on the date of clutch initiation, nest predation and clutch size in the Red-backed Shrike was not found, but such an influence on the number of nestlings was shown. The minimum adequate model explained 18.3% of the variation between territories in nestling’s number. The number of fledglings was positively correlated with the area of pastures, meadows, orchards and fallows within territories, and negatively correlated with length of overhead transmission lines. The number of fledglings was correlated with food abundance within territories, based on to the results from pitfall traps. There was no correlation between territory food abundance and the size of clutch. The presence of pastures, meadows and fallows, which are foraging places, thus seems to be crucial for the protection of the Red-backed Shrike.     

Woodlarks Lullula arborea and landscape heterogeneity created by land abandonment

Capsule Fine‐grained landscape heterogeneity may be a major factor in the recent expansion of Woodlark populations.

Aim To determine the factors which may have led to the increase in Woodlark populations in the Mediterranean region.

Methods Woodlark habitat selection was determined using territory mapping in an area that had undergone widespread land abandonment during the past 50 years. Remote sensing data were used to study landscape changes within the study area between 1978 and 2003.

Results Most Woodlark territories included a combination of farmland and shrubland patches. These fulfilled the birds’ requirements for territorial display and for foraging. Land abandonment has increased the availability of open shrubland, the dominant land‐cover type selected by Woodlarks.

Conclusions Increased fine‐grained landscape heterogeneity following farm abandonment has created opportunities for habitat use by Woodlarks and may be a major factor in the Woodlark population expansion observed between 1978 and 2003.     

Habitat associations and breeding success of the Chaffinch Fringilla coelebs

Capsule Population trends for Chaffinch on farmland are unlikely to be explained by their preference for non-crop habitats alone.

Aims To investigate the importance of non-cropped habitats for Chaffinch territory distribution, breeding success and foraging habitat selection in Scottish farmland.

Methods Territory distribution, nesting success and foraging behaviour of adults feeding chicks at the nest were recorded and related to habitat composition on two Scottish lowland farms.

Results Higher Chaffinch territory densities were associated with the presence of hedgerows, trees and grass leys, whereas lower densities were found adjacent to winter Barley. Nests were predominantly located in conifer trees and hedgerows. Trees were selected preferentially for foraging. Poor breeding success was detected in nests associated with cereal crops and wider field margins. Farmland in Scotland supported much lower territory densities than in England.

Conclusion Chaffinches rely predominantly on non-cropped habitats for territory establishment, nesting and foraging habitats. Differences in habitat composition between England and Scotland may explain differences in territory densities. However, the Chaffinch's preference for non-crop habitats is unlikely to explain its population trends alone. Immigration from other habitats and/or a decrease in inter-specific competition for resources may also have contributed to the increase in the national farmland Chaffinch population.     

Identification of Lanius species and subspecies using tandem repeats in the mitochondrial DNA control region

The number of tandem repeats in the mitochondrial control region were used to differentiate the Red-backed Shrike Lanius collurio , Woodchat Shrike Lanius senator , Great Grey Shrike (subspecies Lanius excubitor excubitor ) and the Southern Grey Shrike (subspecies L. meridionalis meridionalis , L. m. koenigi, L. m. pallidirostris and L. m. aucheri ). The Red-backed and Woodchat Shrikes lacked repeats whereas the Great Grey and Southern Grey had two, three and 2 + 3 repeats. A subspecies of Southern Grey ( L. m. koenigi ) had 2 + 3 + 4 repeats. These findings are discussed in terms of the taxonomy of the Lanius genus, especially with respect to the Great Grey and Southern Grey Shrikes.     

Conservation potential of semi-natural habitats for birds in intensively-used agricultural landscapes

Agricultural intensification resulted in substantial loss of farmland biodiversity. Semi-natural habitats may be viewed as potential buffers of these adverse impacts, but a rigorous assessment of their capacity for supporting farmland biodiversity is lacking. In this study, we explored conservation potential of two different types of semi-natural habitats for birds in intensively-used agricultural landscapes – farmland hedges (i.e., linear strips of shrubby and tree vegetation) and open scrubland (i.e., scattered shrubs and abandoned orchards). Specifically, we tested whether the abundance and species richness of birds differ between these habitats considering various species traits, such as habitat affinity (i.e., forest, farmland and urban species), diet specialization (i.e., animal eaters, plant eaters, and omnivores) and conservation status (Species of European Conservation Concern). We found that open scrubland hosted on average 37.9 bird species and 122.6 individuals per 1 km² of the transect, whereas farmland hedges hosted only 19 species and 61.8 individuals per 1 km² of the transect. However, results have substantially changed if we considered the area of suitable habitat into account. More specifically, open scrubland hosted more bird species and individuals when we considered open habitat species and the area of open habitats, whereas farmland hedges had higher species diversity and individuals of woodland bird species when we considered the area of woodland habitats. Similarly, analyses of habitat affiliations of individual species corresponded to the whole-community patterns; and revealed that several woodland bird species were mainly associated with farmland hedges (e.g., Chaffinch Fringilla coelebs, Common Nightingale Luscinia megarhynchos and Blackcap Sylvia atricapilla), whereas the open scrubland was preferred by open habitat bird species (e.g., Corn Bunting Emberiza calandra, Quail Coturnix coturnix and Skylark Alauda arvensis). These results demonstrate that semi-natural habitats, both open scrubland and farmland hedges, have large potential for promotion and conservation of bird communities within intensively used agricultural landscapes, as both may have represented suitable habitats for species with different ecological requirements. Therefore, management measures focused on the enlargement of the area of these habitats, in combination with suitable management (e.g., regulating the progress of natural succession in open scrubland; increasing structural diversity of existing farmland hedges), may substantially contribute to bird conservation within agricultural landscapes.     

Effects of habitat use on food acquisition and food caching during a nonbreeding season in a winter-breeding,food-storing passerine

ABSTRACT

Capsule: Wintering male Bull-headed Shrikes Lanius buchepalus preferred vegetable fields with perch sites to search for and detect terrestrial prey, and males occupying territories with large areas of vegetable fields acquired more prey and cached more food.

Aims: To better understand effects of habitat use on food acquisition and food caching of the Bull-headed Shrike, we investigated relationships between habitat quality (measured through foraging-site selection and foraging success) and food caching during the non-breeding season.

Methods: We monitored 66 territorial male shrikes during the non-breeding season from 2014 to 2016, and collected data on foraging-site selection, foraging success, and food caching.

Results: Our field observations showed that male shrikes preferred to forage over vegetable fields and that males occupying territories incorporating large areas of that habitat were able to acquire more food items and store more food caches in their territories during the nonbreeding season.

Conclusion: We suggest that for male Bull-headed Shrikes, a winter-breeding food-storing passerine, the quality of habitat in the nonbreeding season has the potential to affect their subsequent fitness.     

Comparison of land cover and farming intensity-based models for mapping High Nature Value farmland in Cyprus

ABSTRACT

Capsule: Breeding bird survey data were used to compare biodiversity at sites defined as High Nature Value farmland (HNVf) under two different mapping models.

Aims: To examine whether farmland classified as HNVf was important for bird diversity and conservation of priority bird species in Cyprus, through comparison of two different HNVf maps. The HNV concept aims to define biodiversity-rich farmland and facilitate its protection and management. Heterogeneous, low-intensity cropping and grazing systems are important areas for biodiversity conservation in Europe and for birds in particular, but are threatened by abandonment and agricultural intensification. We compared two HNVf mapping systems, a simpler model based on land cover data (CLC map) and a more complex Cyprus Environment Department model (ED map) including layers relating to agricultural intensity.

Methods: Line transect bird surveys were carried out to compare bird diversity, abundance of farmland bird species of conservation priority and also of the endemic Cyprus Warbler Sylvia melanothorax, at sites classified as HNV or not.

Results: A greater diversity of breeding birds was found in sites classified as HNVf under combined ED and CLC maps. However, for the set of 12 priority bird species, neither HNV mapping approach encompassed their overall abundance, but a combined CLC and ED model did predict higher abundances of the Cyprus Warbler. Vineyard sites were found to be associated with high overall breeding bird diversity, but with low abundance of priority bird species.

Conclusion: We identified weaknesses in both mapping systems, with the ED model failing to capture all HNV grazing land and the CLC model defining some intensive farming systems as HNV. We conclude that the overlap between the two models best captures HNVf, but layers encompassing grazing land and priority habitats need to be added to better define HNVf in Cyprus and facilitate its protection and management.     

Habitat associations of British breeding farmland birds

Capsule Territory distribution for ten species was most strongly positively influenced by the presence of hedges and woodland edge.

Aims To describe and rank the importance of different habitat predictors on the distribution of bird territories.

Methods We derived territory maps for ten bird species across 25 sites on English lowland farmland in 2002. We related habitat predictors to the distribution of these species using information theoretic methods.

Results Habitat predictors were ranked as follows (numbers in parentheses indicate the number of species with a strong effect): hedge presence (8), boundary height (7), woodland edge (6), tree presence in boundary (4), brassica (mainly oil seed rape) (3), within‐field vegetation height (3), boundary strip (3), boundary width (3), tilled fields (3), winter set‐aside (2), ditch (1), winter stubble fields (1).

Conclusions Non‐cropped habitats had the most consistent positive effects across all ten species, with crop types and their margins exerting smaller effects.     

Fine‐scale habitat use during the non‐breeding season suggests that winter habitat does not limit breeding populations of a declining long‐distance Palearctic migrant

For migrant birds, which habitats are suitable during the non‐breeding season influences habitat availability, population resilience to habitat loss, and ultimately survival. Consequently, habitat preferences during winter and whether habitat segregation according to age and sex occurs directly influences migration ecology, survival and breeding success. We tested the fine‐scale habitat preferences of a declining Palearctic migrant, the whinchat Saxicola rubetra, on its wintering grounds in west Africa. We explored the influence of habitat at the territory‐scale and whether dominance‐based habitat occupancy occurs by describing the variation in habitat characteristics across wintering territories, the degree of habitat change within territories held throughout winter, and whether habitat characteristics influenced territory size and space‐use within territories or differed with age and sex. Habitat characteristics varied substantially across territories and birds maintained the same territories even though habitat changed significantly throughout winter. We found no evidence of dominance‐based habitat occupancy; instead, territories were smaller if they contained more perching shrubs or maize crops, and areas with more perching shrubs were used more often within territories, likely because perches are important for foraging and territory defence. Our findings suggest that whinchats have non‐specialised habitat requirements within their wintering habitat of open savannah and farmland, and respond to habitat variation by adjusting territory size and space‐use within their territories instead of competing with conspecifics. Whinchats show a tolerance for human‐modified habitats and results support previous findings that some crop types may provide high‐quality wintering habitat by increasing perch density and foraging opportunities. By having non‐specialised requirements within broad winter habitat types, migrants are likely to be flexible to changing wintering conditions in Africa, both within and across winters, so possibly engendering some resilience to the rapid anthropogenic habitat degradation occurring throughout their wintering range.     

The Crested Lark Galerida cristata as an example of a bird species that benefits from agricultural management in western Poland

ABSTRACT

Capsule: The Crested Lark Galerida cristata as an example of a species which selects habitats which have undergone agricultural intensification.

Aims: To describe habitat preferences of the Crested Lark in western Poland.

Methods: We surveyed 30 randomly chosen study plots (1?km²) in western Poland to detect breeding pairs of Crested Larks. Sentinel and direct observations in the field were used to provide habitat data. Generalized linear mixed models were used to determine what type of environments habitats were selected by the Crested Larks.

Results: We recorded a total of 106 pairs of Crested Larks in 30 study plots. Birds inhabited farmland environments, where their preferred habitats included buildings, silage, and arable land with cereals.

Conclusion: Silage, which is associated with agricultural intensification within agricultural landscapes, increased the chances of the occurrence of Crested Larks.     

Structural heterogeneity of linear habitats positively affects Barred Warbler Sylvia nisoria,Common Whitethroat Sylvia communis and Lesser Whitethroat Sylvia curruca in farmland of Western Poland

Capsule Structural heterogeneity was the most important factor influencing the distribution of Barred Warbler Sylvia nisoria, Common Whitethroat S. communis and Lesser Whitethroat S. curruca in linear habitats in farmland of Western Poland.

Aims To investigate the occurrence of three species of Sylvia warblers in relation to the spatial structure of linear habitats in the agricultural landscape of Western Poland where, in contrast to Western Europe, field boundaries are not managed in terms of their size or spatial structure.

Methods In 2008, the distribution of breeding territories of Sylvia warblers in linear habitats was estimated in farmland of Western Poland. Redundancy detrended analysis was used to assess the relationship between bird abundance and seven linear habitat variables in ninety-four 150?m sections.

Results Sylvia warblers differed in habitat requirements, however heterogeneity affected their distribution to the greatest extent. In addition, Barred Warbler preferred high shrub volume and wider sections, whereas Common Whitethroat was attracted by brambles and nettles and Lesser Whitethroat favoured shrubs. All species avoided a high proportion of low vegetation.

Conclusion Structural heterogeneity resulted in highly preferred linear habitats for Sylvia warblers. Thus, maintaining or increasing structural heterogeneity of linear habitats may be a very effective tool for the conservation of farmland bird populations.     

Reproductive success of Woodlarks Lullula arborea in traditional and recently colonized habitats

Capsule Set-aside schemes have allowed breeding Woodlarks to colonize farmland, but heathland and forestry habitats remain the stronghold.

Aims To determine which habitats provide the best conditions for breeding Woodlarks and whether a buffer effect is operating, with density increasing faster in the poorer quality habitat as the population grows.

Methods Habitat colonization was examined and breeding success compared among heathland, clear-felled and young conifer plantations, and farmland set-aside.

Results Woodlarks on heathland and forestry habitats had similar clutch sizes and nesting success, but clutch sizes may be lower on farmland. Heathland was recolonized when population density was low in forest habitats, while farmland was colonized when density was increasing, and areas close to forest were preferentially occupied. Woodlarks breeding on farmland preferred set-aside stubbles to other field types.

Conclusion Forestry and heathland habitats are similar in quality for breeding Woodlarks, with no evidence for a buffer effect. Farmland set-aside may be suboptimal but the area available is much greater than the area of forest or heathland, and could therefore make a significant contribution to the conservation of the Woodlark population. However, set-aside should not be seen as an alternative to the conservation of forest and heathland.     

Storing prey in larders affects nestling haematological condition in the Red-backed Shrike (Lanius collurio)

Many animals, including shrikes (Laniidae), are known to store food. This behaviour ensures food availability during inclement weather, for rearing nestlings or signalling territory quality. Unlike most other shrike species, which accumulate food before breeding, Red-backed Shrikes Lanius collurio store food in larders, mainly during the nestling and fledgling periods. If this is an adaptive behaviour, variation in this behaviour should affect either or both the number and condition of nestlings, which may benefit from such larders. We assessed the haematological condition of Red-backed Shrike nestlings in east-central Poland in 2021 using a suite of blood parameters relating to sites where shrikes did or did not store food. Haemoglobin concentrations were positively correlated with larders, being significantly higher in nestlings of pairs that stored prey compared with those whose parents did not do so. White blood cell counts were lower in nestlings whose parents kept larders. Red blood cell counts and glucose concentrations in nestlings were not related to whether parents had larders. Food storage probably ensures a more constant access to food, which results in a superior haematological condition in nestlings.     

The impact of forest encroachment after agricultural land abandonment on passerine bird communities: The case of Greece

Agricultural land abandonment is one of the main drivers of land use change, leading to various responses of farmland ecological communities. In an effort to better understand the effect of agricultural land abandonment on passerine bird communities, we sampled 20 randomly selected sites [1 km × 1 km] in remote Greek mountains, reflecting an abandonment gradient, in terms of forest encroachment. We sampled 169 plots using the point count method of fixed distance (47 passerine species), and we investigated bird diversity and community structure turnover along the gradient. We found that grazing intensity has a beneficial effect hampering forest encroachment that follows progressively land abandonment. Habitat composition changes gradually with forests developing at the expense of open meadows and heterogeneous grasslands. Forest encroachment has a significant negative effect on bird diversity and species richness, affecting in particular typical farmland and Mediterranean shrubland species. Birds form five distinct ecological clusters after land abandonment: species mostly found in pinewoods and cavity-dwelling species; species that prefer open forests forest edges or ecotones; species that prefer shrubland or open habitats with scattered woody vegetation; Mediterranean farmland birds that prefer semi-open habitats with hedges and/or woodlots; and, generalist forest-dwelling or shrubland species. We extracted a set of 22 species to represent the above ecological communities, as a new monitoring tool for agricultural land use change and conservation. We suggest that the maintenance of rural mosaics should be included in the priorities of agricultural policy for farmland bird diversity conservation.     

Traditional farming and key foraging habitats for chough Pyrrhocorax pyrrhocorax conservation in a Spanish pseudosteppe landscape

1. Agricultural land devoted to low-intensity practices supports many declining bird species in Europe. The potential effects of intensification or abandonment of traditional farming practices are assessed from the point of view of the conservation of the chough Pyrrhocorax pyrrhocorax .
2. The study was conducted in Los Monegros (north-east Spain), in a pseudosteppe landscape of special relevance for this species. In this area traditional farming survives in the form of low-intensity arable systems including fallowing and extensive sheep grazing.
3. Foraging choughs showed a strong selection for field margins, avoided any remnant of the original scrubland and halophitic vegetation, and utilized other habitats maintained by traditional crop rotation (e. g. fallow, stubble) at different times of the year.
4. A highly complex pattern of habitat selection was found which was not only related to seasonal changes in habitat availability, but also differed between territorial pairs and the non-breeding population. This emphasizes the importance of taking all the different components of bird populations into account when analysing interactions between habitat selection and the annual farming cycle.
5. Chough habitat selection suggests that both agricultural intensification and land abandonment would have detrimental consequences for this species in Los Monegros. The maintenance of traditional farming is recommended, especially by promoting the use of long fallow rotations grazed extensively by livestock, encouraging the increase of grassland edges around landholdings and sand roads, and maintaining a low input of biocides. These management measurements could also favour most other endangered species of steppe birds, and could be supported by the establishment of Zonal Programmes under the CAP Agri-Environment Regulation (2078/92).     

Bird communities of highway verges: Influence of adjacent habitat and roadside management

We have investigated the effects of landscape traversed and roadside structure on the use of highway verges by birds. Three contrasted landscapes were chosen in terms of human land use and vegetation structure: an intensive farmland, a pine plantation, and a matoral. The roadside sections varied in vegetation structure, width and profile. We recorded birds present in roadsides and adjacent habitats by transect counts over all seasons. Roadside bird species appeared for a great part similar to those of adjacent habitats. However, diversity and abundance in verges did not depend on that of adjacent habitats. Woody roadsides were comparable to hedges, as trees (and shrubs) in verges enhanced species richness and abundance of birds in the farmland and woodland sites. Width and profile of verges had less influence. In all sites, typical species of the habitat traversed partly avoided roadsides. On the contrary, numerous species associated with ‘rare’ habitats in one site preferred roadsides, provided that verge vegetation contrasted with the dominant habitat. It is concluded that birds responses to highways can vary greatly with landscape traversed and verge vegetation. Highway verges could be favorable to birds, if they constitute a complementary habitat to the dominant habitat within a landscape.     

Patchy versus linear non-cropped habitats in farmland: which is better for nesting success of the Red-backed Shrike Lanius collurio?

Capsule: The survival rate of Red-backed Shrike Lanius collurio nests in western Poland was higher when they nested in bushes aggregated in patches, rather than linear formations.