Shelley A. Hinsley

Habitat and landscape factors influencing the presence of individual breeding bird species in woodland fragments

Bird species distributions in 151 woods (0.02-30 ha) in a lowland arable landscape in eastern England were investigated using logistic regression analysis. Of 31 species included in the study, only Marsh Tit Parus palustris, Nightingale Luscinia megarhynchos and Chiffchaff Phylloscopus collybita failed to breed in woods of <0.5 ha. For many woodland species, the probability of breeding was positively related to woodland area and other variables decribing the woods themselves. For other species, including Blackbird Turdus merula and Sparrowhawk Accipiter nisus, woodland perimeter, rather than area, was significant. Variables describing the landscape surrounding the woods were important for both woodland species and those more typical of open country. The length of hedgerow in the surrounding landscape was positively related to the breeding presence in particular woods of Long-tailed Tit Aegithalos caudatus, Robin Erithacus rubecula, Bullfinch Pyrrhula pyrrhula, Garden Warbler Sylvia borin and Blackcap Sylvia atricapilla, and the area of surrounding woodland was important for Long-tailed Tit, Great-spotted Woodpecker Dendrocopos major and Chaffinch Fringilla coelebs. The presence of Treecreeper Certhia familiaris was negatively related to the distance to the nearest wood, whereas that of Tree Sparrow Passer montanus was negatively related to the amount of woodland in the surrounding landscape. Thus species breeding distributions were influenced by factors associated with the wider landscape, on a scale larger than that of their immediate habitats.

Factors influencing bird species numbers in small woods in south-east England

151 woods, ranging in size from 0.02 to 30 ha and with differing degrees of isolation, were surveyed to determine the numbers of breeding bird species present in each of three consecutive years. Woodland and edge species were analysed separately. Numbers of woodland species showed a strong relationship with woodland area which explained c. 70% of the variation in breeding species numbers. Several other features of the woods and of the surrounding landscape also had small additional influences on species numbers. Numbers of edge species showed a poor relationship with woodland area, but length of perimeter explained 30-40% of the variation in species numbers. The number of structural features within a wood and isolation from other woodland also had small additional positive influences on edge species numbers. Small woods held more edge species than equivalent areas of large woods, but tended to hold fewer woodland species than equivalent areas of large woods.

Remote sensing and the future of landscape ecology

Landscape ecology focuses on the analysis of spatial pattern and its relationship to ecological processes. As a scientific discipline, landscape ecology has grown rapidly in recent years, supported by developments in GIS and spatial analysis techniques. Although remote sensing data are widely employed in landscape ecology research, their current and potential roles have not been evaluated critically. To provide an overview of current practice, 438 research papers published in the journal Landscape Ecology for the years 2004—2008 were examined for information about use of remote sensing. Results indicated that only 36% of studies explicitly mentioned remote sensing. Of those that did so, aerial photographs and Landsat satellite sensor images were most commonly used, accounting for 46% and 42% of studies, respectively. The predominant application of remote sensing data across these studies was for thematic mapping purposes. This suggests that landscape ecologists have been relatively slow to recognize the potential value of recent developments in remote sensing technologies and methods. The review also provided evidence of a frequent lack of key detail in studies recently published in Landscape Ecology , with 75% failing to provide any assessment of uncertainty or error relating to image classification and mapping. It is suggested that the role of remote sensing in landscape ecology might be strengthened by closer collaboration between researchers in the two disciplines, by greater integration of diverse remote sensing data with ecological data, and by increased recognition of the value of remote sensing beyond land-cover mapping and pattern description. This is illustrated by case studies drawn from Latin America (focusing on forest loss and fragmentation) and the UK (focusing on habitat quality for woodland birds). Such approaches might improve the analytical and theoretical rigour of landscape ecology, and be applied usefully to issues of outstanding societal interest, such as the impacts of environmental change on biodiversity and ecosystem services.

Wildlife-friendly farming increases crop yield: evidence for ecological intensification.

Ecological intensification has been promoted as a means to achieve environmentally sustainable increases in crop yields by enhancing ecosystem functions that regulate and support production. There is, however, little direct evidence of yield benefits from ecological intensification on commercial farms growing globally important foodstuffs (grains, oilseeds and pulses). We replicated two treatments removing 3 or 8% of land at the field edge from production to create wildlife habitat in 50–60 ha patches over a 900 ha commercial arable farm in central England, and compared these to a business as usual control (no land removed). In the control fields, crop yields were reduced by as much as 38% at the field edge. Habitat creation in these lower yielding areas led to increased yield in the cropped areas of the fields, and this positive effect became more pronounced over 6 years. As a consequence, yields at the field scale were maintained—and, indeed, enhanced for some crops—despite the loss of cropland for habitat creation. These results suggested that over a 5-year crop rotation, there would be no adverse impact on overall yield in terms of monetary value or nutritional energy. This study provides a clear demonstration that wildlife-friendly management which supports ecosystem services is compatible with, and can even increase, crop yields.

Influence of Woodland Area on Breeding Success in Great Tits Parus major and Blue Tits Parus caeruleus

Reproductive performance of Great Tits and Blue Tits breeding in highly fragmented woodland was investigated in relation to woodland area in a landscape dominated by intensive arable agriculture in eastern England. Breeding performance was recorded for five years (1993-1997) for tits breeding in nestboxes in up to 43 woods ranging in size from 0.1 to 157 ha. Trends in the components of breeding success with woodland area were investigated using a linear, mixed model including both fixed and random effects, and logistic regression analysis. In both Great Tits and Blue Tits, breeding performance declined with decreasing woodland area. For Blue Tits, the decline was accounted for by the timing of breeding which was later in smaller woods. Great Tits showed a similar trend in laying date with woodland area, but over and above this effect of timing on breeding success, they also reared lighter young in smaller woods. The variation in first egg date accounted for by woodland area was about 25% for Great Tits and 33% for Blue Tits. In some years, failure at the nestling stage was frequent for Great Tits (but not Blue Tits) in small woods, but was not recorded to the same extent in large woods. The results are discussed in the context of previous studies of tit breeding success in relation to individual bird quality, habitat quality and availability, and the consequences of habitat fragmentation.

Influences of population size and woodland area on bird species distributions in small woods

Distributions of individual bird species in 151 small woods (size range 0.02–30 ha) were investigated in 3 consecutive years during which the abundance of certain species varied markedly. Relationships between the probabilities of certain bird species breeding and woodland area were described using incidence functions derived from logistic regression analysis. In general, for species which were largely dependent on woodland and seldom occurred in other habitats (such as hedgerows and gardens), the probability of breeding approached 100% only for woods of 10 ha and more, whereas species with less stringent habitat requirements occurred in the majority of woods, including those of 1 ha and less. The sensitivity of incidence functions to changes in regional abundance and the size distribution of the study woods was examined. For some species, distribution patterns could not be distinguished from those expected if pairs had been distributed in proportion to woodland area (random placement), but the majority did not conform to random placement in at least 1 of the 3 years. This nonconformity was consistent across all 3 years for some species, such as wren (Troglodytes troglodytes), despite substantial fluctuations in population sizes between years, while for others, such as robin (Erithacus rubecula), distribution patterns changed with changes in regional abundance. The results suggested that some species, such as wren and blackbird (Turdus merula), preferred small woods, while other species, such as chiffchaff (Phylloscopus collybita), preferred large woods. For several other species, including robin, great tit (Parus major), long-tailed tit (Aegithalos caudatus) and marsh tit (P. palustris), small woods appeared to be sub-optimal under at least some conditions.

Wildlife-friendly farming benefits rare birds, bees and plants

Agricultural intensification is a leading cause of global biodiversity loss, especially for threatened and near-threatened species. One widely implemented response is ‘wildlife-friendly farming’, involving the close integration of conservation and extensive farming practices within agricultural landscapes. However, the putative benefits from this controversial policy are currently either unknown or thought unlikely to extend to rare and declining species. Here, we show that new, evidence-based approaches to habitat creation on intensively managed farmland in England can achieve large increases in plant, bee and bird species. In particular, we found that habitat enhancement methods designed to provide the requirements of sensitive target biota consistently increased the richness and abundance of both rare and common species, with 10-fold to greater than 100-fold more rare species per sample area than generalized conventional conservation measures. Furthermore, targeting landscapes of high species richness amplified beneficial effects on the least mobile taxa: plants and bees. Our results provide the first unequivocal support for a national wildlife-friendly farming policy and suggest that this approach should be implemented much more extensively to address global biodiversity loss. However, to be effective, these conservation measures must be evidence-based, and developed using sound knowledge of the ecological requirements of key species.

The Application of Lidar in Woodland Bird Ecology

Habitat quality is fundamental in ecology, but is difficult to quantify. Vegetation structure is a key characteristic of avian habitat, and can play a significant role in influencing habitat quality. Airborne lidar provides a means of measuring vegetation structure, supplying accurate data at high post-spacing and on a landscape-scale, which is impossible to achieve with field-based methods. We investigated how climate affected habitat quality using great tits (Parus major) breeding in woodland in eastern England. Mean chick body mass was used as a measure of habitat quality. Mean canopy height, calculated from a lidar digital canopy height model, was used as a measure of habitat structure. The influence of canopy height on body mass was examined for seven years during which weather conditions varied. The slopes and correlation coefficients of the mass/height relationships were related linearly to the warmth sum, an index of spring warmth, such that chick mass declined with canopy height in cold, late springs, but increased with height in warm, early springs. The parameters of the mass/height relationships, and the warmth sum, were also related linearly to the winter North Atlantic Oscillation index, but with a time lag of one year. Within the same wood, the structure conferring “best” habitat quality differed between years depending on weather conditions.

Local extinctions and recolonisations of passerine bird populations in small woods

This paper considers, for eight species of woodland bird, the factors that influenced both local extinctions and recolonisations in 145 woods over 3 years. In all species, probability of local extinction was inversely related to population size; most local extinctions occurred in woods containing one to three breeding pairs. However, considerable variation in extinction probabilities occurred between species and between years. In addition, the suitability of habitat within a wood (more extinctions in less suitable woods) was important for wren Troglodytes troglodytes, song thrush Turdus philomelos and blue tit Parus caeruleus; also, the structure of the surrounding landscape was important for blue tit, great tit Parus major, and chaffinch Fringilla coelebs (more extinctions in localities with less woodland). In only two species was the probability of recolonisation related to any of the measured variables. Wrens were more likely to recolonise larger woods, whereas song thrushes were more likely to recolonise woods with a high habitat suitability rating and those which are more isolated from other woodland

Influences of Habitat Fragmentation on Bird Species Distributions and Regional Population Sizes

A simple modelling approach was used to investigate the influence of habitat fragmentation on the distributions and regional population sizes of passerines breeding in 145 small woods in an arable landscape. Observed distributions in three consecutive years were compared with those predicted by random selection of woods by pairs (based on a Poisson distribution), and by a simulation model based on the area of habitat available and estimates of individual species minimum area requirements and territory sizes. None of the species studied were distributed randomly; some were distributed according to the area of woodland available, whereas others preferred either small or large woods. However, species distributions were influenced by their regional population sizes. When species population sizes were small, observed distributions could be predicted using algorithms based on area alone, but as numbers increased, algorithms using territory parameters were required. An absence of detectable territorial interaction suggested that space for more pairs of the species concerned had been available in our woods. Of the 14 species investigated, the models for only two consistently required the use of territory parameters, indicating that the available habitat could probably have accommodated more pairs of most of the species. Thus habitat fragmentation may reduce regional population sizes more than expected from the loss of habitat alone, to the extent that patches of suitable habitat may be unused, or occupied at low density.