Malcolm D. Burgess

Global hotspots of species richness are not congruent with endemism or threat

Biodiversity hotspots have a prominent role in conservation biology, but it remains controversial to what extent different types of hotspot are congruent. Previous studies were unable to provide a general answer because they used a single biodiversity index, were geographically restricted, compared areas of unequal size or did not quantitatively compare hotspot types. Here we use a new global database on the breeding distribution of all known extant bird species to test for congruence across three types of hotspot. We demonstrate that hotspots of species richness, threat and endemism do not show the same geographical distribution. Only 2.5% of hotspot areas are common to all three aspects of diversity, with over 80% of hotspots being idiosyncratic. More generally, there is a surprisingly low overall congruence of biodiversity indices, with any one index explaining less than 24% of variation in the other indices. These results suggest that, even within a single taxonomic class, different mechanisms are responsible for the origin and maintenance of different aspects of diversity. Consequently, the different types of hotspots also vary greatly in their utility as conservation tools.

Direct versus indirect sexual selection: genetic basis of colour, size and recruitment in a wild bird

Indirect and direct models of sexual selection make different predictions regarding the quantitative genetic relationships between sexual ornaments and fitness. Indirect models predict that ornaments should have a high heritability and that strong positive genetic covariance should exist between fitness and the ornament. Direct models, on the other hand, make no such assumptions about the level of genetic variance in fitness and the ornament, and are therefore likely to be more important when environmental sources of variation are large. Here we test these predictions in a wild population of the blue tit (Parus caeruleus), a species in which plumage coloration has been shown to be under sexual selection. Using 3 years of cross-fostering data from over 250 breeding attempts, we partition the covariance between parental coloration and aspects of nestling fitness into a genetic and environmental component. Contrary to indirect models of sexual selection, but in agreement with direct models, we show that variation in coloration is only weakly heritable , and that two components of offspring fitness—nestling size and fledgling recruitment—are strongly dependent on parental effects, rather than genetic effects. Furthermore, there was no evidence of significant positive genetic covariation between parental colour and offspring traits. Contrary to direct benefit models, however, we find little evidence that variation in colour reliably indicates the level of parental care provided by either males or females. Taken together, these results indicate that the assumptions of indirect models of sexual selection are not supported by the genetic basis of the traits reported on here.

Large-scale variation in the temporal patterns of the frass fall of defoliating caterpillars in oak woodlands in Britain: implications for nesting woodland birds

Capsule Frass fall was later and of longer duration in woods to the north and west of Britain compared with those in the southeast. Aims Defoliating caterpillars are a major food resource for woodland breeding birds and our aims were to quantify large-scale patterns in the timing and duration of the spring peak in abundance of these caterpillars in oak woodlands in Britain. Methods We deployed traps to collect caterpillar frass at regular intervals through spring in 19 oak woods distributed through England, Wales and Scotland. Models of the temporal patterns of the rate of frass fall were used to explore relationships with geographic variables and average local temperature. Results The date of peak frass fall in 2010 ranged from 20 May to 18 June and was significantly related to altitude, latitude and local April–May temperature. The duration of the peak ranged from 20 to 53 days and was correlated with the date of the peak and April–May temperature. Limited data from 2008 and 2009 indicated considerable between-year variation in the date of the peak, which was consistent with the relationship with local temperature found in 2010. Conclusions The date of peak frass fall was later and the duration of the peak longer in the north and west of Britain compared with the southeast which will have considerable implications for nesting woodland birds such as Pied Flycatchers. The date of the peak was well modelled by local April–May temperature offering the prospect of good predictive models. However, the duration of the peak was less well modelled by local temperature and may be determined by other factors.

Restricted dispersal reduces the strength of spatial density dependence in a tropical bird population

Spatial processes could play an important role in density-dependent population regulation because the disproportionate use of poor quality habitats as population size increases is widespread in animal populations—the so-called buffer effect. While the buffer effect patterns and their demographic consequences have been described in a number of wild populations, much less is known about how dispersal affects distribution patterns and ultimately density dependence. Here, we investigated the role of dispersal in spatial density dependence using an extraordinarily detailed dataset from a reintroduced Mauritius kestrel (Falco punctatus) population with a territorial (despotic) breeding system. We show that recruitment rates varied significantly between territories, and that territory occupancy was related to its recruitment rate, both of which are consistent with the buffer effect theory. However, we also show that restricted dispersal affects the patterns of territory occupancy with the territories close to release sites being occupied sooner and for longer as the population has grown than the territories further away. As a result of these dispersal patterns, the strength of spatial density dependence is significantly reduced. We conclude that restricted dispersal can modify spatial density dependence in the wild, which has implications for the way population dynamics are likely to be impacted by environmental change.

Sympatric divergence and clinal variation in multiple coloration traits of Ficedula flycatchers

Geographic variation in phenotypes plays a key role in fundamental evolutionary processes such as local adaptation, population differentiation and speciation, but the selective forces behind it are rarely known. We found support for the hypothesis that geographic variation in plumage traits of the pied flycatcher Ficedula hypoleuca is explained by character displacement with the collared flycatcher Ficedula albicollis in the contact zone. The plumage traits of the pied flycatcher differed strongly from the more conspicuous collared flycatcher in a sympatric area but increased in conspicuousness with increasing distance to there. Phenotypic differentiation (PST) was higher than that in neutral genetic markers (FST), and the effect of geographic distance remained when statistically controlling for neutral genetic differentiation. This suggests that a cline created by character displacement and gene flow explains phenotypic variation across the distribution of this species. The different plumage traits of the pied flycatcher are strongly to moderately correlated, indicating that they evolve non‐independently from each other. The flycatchers provide an example of plumage patterns diverging in two species that differ in several aspects of appearance. The divergence in sympatry and convergence in allopatry in these birds provide a possibility to study the evolutionary mechanisms behind the highly divergent avian plumage patterns.

The impact of changing habitat availability on population trends of woodland birds associated with early successional plantation woodland

Capsule Trends in young woodland availability influenced population trends and abundance of Tree Pipit and Lesser Redpoll, but not 10-km square occupancy. Aims To investigate whether changes in availability of young woodland could have driven population change, and trends in abundance and occupancy, of declining Tree Pipit and Lesser Redpoll populations in Britain. Methods Modelling approaches used annual population indices and woodland planting statistics. Abundance and occupancy change between two bird atlases were examined in relation to changes in woodland availability from two woodland inventories. Results English declines were strongly associated with decreases in young coniferous woodland availability and less strongly with increases in young broadleaved woodland. Abundance was related to the area of young woodland in corresponding 10-km squares. Young woodland availability declined between forest inventories and species occupancy maintained in 10-km squares with more young woodland; however squares that showed retention or increases in occupancy showed higher reductions in woodland. Conclusion We suggest declining availability of young coniferous woodland contributed to Tree Pipit and Lesser Redpoll population trends in England. Although likely to be the case in Scotland and Wales, the lack of sufficient temporal data inhibited our ability to test this properly. This work suggests that woodland availability was not the primary driver of Tree Pipit or Lesser Redpoll population trends.

Investigating the practicality of using radio tracking to determine home range and movements of Picathartidae

Radiotelemetry is an important tool used to aid the understanding and conservation of cryptic and rare birds. The two bird species of the family Picathartidae are little-known, secretive, forest-dwelling birds endemic to western and central Africa. In 2005, we conducted a radio-tracking trial of Grey-necked Picathartes Picathartes oreas in the Mbam Minkom Mountain Forest, southern Cameroon, using neck collar (two birds) and tail-mounted (four birds) transmitters to investigate the practicality of radio-tracking Picathartidae. Three birds with tail-mounted transmitters were successfully tracked with the fourth, though not relocated for radio tracking, resighted the following breeding season. Two of these were breeding birds that continued to provision young during radio tracking. One neck-collared bird was found dead three days after transmitter attachment and the other neither relocated nor resighted. As mortality in one bird was potentially caused by the neck collar transmitter we recommend tail-mounted transmitters in future radio-tracking studies of Picathartidae. Home ranges, shown using minimum convex polygon and kernel estimation methods, were generally small (<0.5 km2) and centred around breeding sites. A minimum of 60 fixes were found to be sufficient for home range estimation.

Morphology, geographical variation and the subspecies of Marsh Tit Poecile palustris in Britain and central Europe

Capsule All British Marsh Tits belong to subspecies Poecile palustris dresseri, being smaller than nominate P. p. palustris of central Europe. Aims Determining the subspecies of Marsh Tit in Britain to test whether ssp. P. p. palustris occurs in northern England and Scotland, by assessing regional variation in size compared with central European birds. Methods 1147 wing length and 250 tail length measurements from 953 Marsh Tits were compared between eight British locations to test for regional variation. Biometrics were compared between birds from Britain and six locations within the continental European range of ssp. palustris. Results There was no regional variation in wing or tail lengths among British Marsh Tits, indicating that all resident birds belong to ssp. dresseri. There was no evidence supporting the existence of ssp. palustris in northern England. British birds were significantly smaller than those from continental Europe, with proportionately shorter tails, consistent across all age and sex classes. Conclusion All British Marsh Tits should be considered as ssp. dresseri, with ssp. palustris being limited to continental Europe. With no evidence of regional variation in size within Britain, reliable sexing methods based on biometrics could be applied in demographic studies throughout the country.

Wood Warbler Phylloscopus sibilatrix nest provisioning rates are correlated with seasonal caterpillar availability in British Oak Quercus woodlands

Capsule Maximum provisioning rates occurred during the seasonal peak in caterpillar availability, controlling for brood age and time of day. Aims To determine if the seasonal availability of caterpillars influenced Wood Warbler Phylloscopus sibilatrix nest provisioning rates. Methods Remote cameras were used to monitor nest visits at 14 nests in 8 British oak Quercus woodlands during 2013. The timing of the caterpillar peak was estimated by monitoring the production of caterpillar faecal pellets under oak trees. Results Maximum provisioning rates occurred when the date of provisioning coincided with the date of peak caterpillar availability, but the percentage change in provisioning rates during asynchrony was dependent on brood age. Younger broods experienced a greater decline in provisioning rates than older broods during asynchrony. Provisioning rates peaked in the morning and declined during the day, but when caterpillar availability was low there was little within-day variation. Conclusion Provisioning rates show seasonal variation that is correlated with caterpillar availability. Previous studies suggest that Wood Warbler reproductive fitness is independent of synchrony between the breeding cycle and the caterpillar peak, however, the implications for adult fitness are unknown and should be investigated further.

Tritrophic phenological match–mismatch in space and time

Increasing temperatures associated with climate change may generate phenological mismatches that disrupt previously synchronous trophic interactions. Most work on mismatch has focused on temporal trends, whereas spatial variation in the degree of trophic synchrony has largely been neglected, even though the degree to which mismatch varies in space has implications for meso-scale population dynamics and evolution. Here we quantify latitudinal trends in phenological mismatch, using phenological data on an oak–caterpillar–bird system from across the UK. Increasing latitude delays phenology of all species, but more so for oak, resulting in a shorter interval between leaf emergence and peak caterpillar biomass at northern locations. Asynchrony found between peak caterpillar biomass and peak nestling demand of blue tits, great tits and pied flycatchers increases in earlier (warm) springs. There is no evidence of spatial variation in the timing of peak nestling demand relative to peak caterpillar biomass for any species. Phenological mismatch alone is thus unlikely to explain spatial variation in population trends. Given projections of continued spring warming, we predict that temperate forest birds will become increasingly mismatched with peak caterpillar timing. Latitudinal invariance in the direction of mismatch may act as a double-edged sword that presents no opportunities for spatial buffering from the effects of mismatch on population size, but generates spatially consistent directional selection on timing, which could facilitate rapid evolutionary change.Most work on phenological mismatch has focused on temporal trends only. Here, the authors analyse trends in spatial and temporal mismatch between trees, caterpillars and birds in the UK, and find delayed phenology of all species with increasing latitude and little spatial variation in the magnitude of mismatch between caterpillars and birds.