A review of the impacts of corvids on bird productivity and abundance

Corvids are often viewed as efficient predators capable of limiting prey species populations. Despite this widely held belief, a comprehensive review quantifying the effect of corvids on the demography of prey species is lacking. We examine the impacts of crows, ravens Corvus spp. and Eurasian Magpies Pica pica on the population parameters of other bird species. We summarize results from 42 studies, which included 326 explicit evaluations of relationships between a corvid and a potential prey species. Population parameters of studied prey species were categorized as abundance‐related (numbers, nest density) or productivity‐related (nest success, brood size). Information from both experimental removal studies and correlative studies was examined. Combining all studies, no negative influence of corvids on either abundance or productivity of prey species was found in 81% of cases. Negative impacts were significantly more likely in cases examining productivity rather than abundance (46 vs. 10%). Experimental studies that removed only corvid species were significantly less likely to show a positive impact on productivity than those removing corvids alongside other predators (16 vs. 60%). This suggests that the impact of corvids is smaller than that of other predators, or that compensatory predation occurs. The impact of corvids was similar between diverse avian groups (such as gamebirds, passerines and waders; or ground‐nesting and other species). Crows were found to be significantly more likely to have a negative impact on prey species productivity than were Magpies (62 vs. 12%), but no differences were found in relation to prey abundance. We conclude that while corvids can have a negative impact on bird species, their impact is small overall, and nearly five times more frequent for productivity than for abundance. These results suggest that in most cases bird populations are unlikely to be limited by corvid predation and that conservation measures may generally be better targeted at other limiting factors. However, negative impacts were found in a minority of cases, and those may require further investigation to develop management tools to mitigate such impacts where they are of economic or conservation concern.     

A comparison of two methods to establish the prevalence of lead shot ingestion in mallards (Anas platyrhynchos) from The Netherlands

Two collection methods for screening the mallard (Anas platyrhynchos) population in the Netherlands for the ingestion of spent lead shot were compared. One method consisted of examination of gizzards from mallards shot by hunters (n = 2,859) and the other method consisted of examination of gizzards from mallards caught in duck traps (n = 865). The 95% confidence interval of lead shot ingestion in the mallard population estimated by the first method was 1.7 to 2.9% and by the second method 1.1 to 3.1%. These values were not significantly different. From the numbers of lead pellets embedded in the gizzard wall in hunter-killed and trapped mallards it was estimated that at least 22 to 68% of the trapped ducks had been hit by lead shot previously, but survived. Furthermore, this study shows that it is reasonable to assume that a substantial part of the pellets which are identified (in this study and other studies) as ingested, may well have been shot into the gizzard lumen at some time before the birds were actually killed. To avoid lead poisoning in mallards and in raptors depredating waterfowl hit by lead shot, a change to steel shot is advocated.     

Free lunch,may contain lead: scavenging shot small mammals

Scavengers are subsidized by the remains of hunting worldwide. Although most studies focus on carcasses of large mammals, small mammals that have been shot likely provide a significant food subsidy as well, particularly in parts of the western United States. Millions of small mammals are estimated to be shot each year for damage control and recreation, many being left in the field. Despite this prevalence of carrion, and the potential for scavengers to ingest residual lead from bullet fragments, the fate of these carcasses is largely unknown. We deployed remote cameras to observe which scavengers consumed shot ground squirrels (Urocitellus spp.) and black-tailed prairie dogs (Cynomys ludovicianus) in 8 locations across Montana, USA. At least 5 species of mammals and 9 species of birds scavenged, including burrowing owls (Athene cunicularia). Scavengers fully consumed 66% of carcasses and partially consumed 9%. Carcasses lasted an average of 24.5 hours before the first scavenger arrived. Of carcasses that were scavenged, mammals ate 16% and birds ate 84%, with corvids and raptors consuming an equal number of carcasses. Common ravens (Corvus corax) and black-billed magpies (Pica hudsonia) visited the most carcasses and often arrived first. Scavengers consumed only 9% of the carcasses that were partially concealed by being inside a burrow. Overall, our results indicate that a diverse scavenger community consumes shot ground squirrels and black-tailed prairie dogs, and consequently, may be exposed to lead from bullet fragments. © 2019 The Wildlife Society.     

Structure and projected decline of a Karoo dwarf tortoise population

Inconspicuous, secretive, or sparsely distributed species receive relatively little research attention, potentially leading to uncertainty about their status and lack of efforts to conserve them. Karoo dwarf tortoises (Chersobius boulengeri) are endemic to South Africa, spend most of the time in retreats at remote arid locations, and are seldom seen. We conducted a 3-year (2018–2020) mark-recapture study to investigate the size and structure of the only Karoo dwarf tortoise population currently known to exist. The population in the 16-ha core of our study site consisted primarily of adult males and females, at a density of 3.3 individuals/ha. Many individuals had severely worn shells and appeared old. Small individuals (straight carapace length <65 mm) represented just 8% of the population and were mostly recent hatchlings. Overall, tortoises had high estimated survival rates (0.77–0.95; lower 95% confidence limit for the smallest tortoises was 0.16), despite a 15-month drought. The lack of small individuals may reflect low levels of recruitment and population decline. Predation by corvids was an obvious threat to all size classes. We estimated that the local population across the 250-ha study area was 800–900 males and females, and recommend precautionary conservation measures focused on reducing human-subsidized avian predation.     

Hunter feedback of individually marked wild boar <Emphasis Type="Italic">Sus scrofa</Emphasis> L.: dispersal and efficiency of hunting in northeastern Germany

Increasing wild boar (Sus scrofa L.) population densities all over Europe cause severe economic problems. For understanding mechanisms of epidemics, the knowledge of dispersal is required. Thus, we investigated dispersal rates and distances with regard to sex and age of wild boar in southwestern Mecklenburg-Western Pomerania. From 152 marked wild boar, 105 have been registered as dead, of which, 51% were males and 49% females. Forty-five percent were shot as piglets, 41% as yearlings, and 14% as adults. The distance between capture site and site of death ranged between 184 m and 41.5 km. Piglets were shot closer to their capture site (mean distance 1 km) than older animals (mean 4 km), although this difference was only significant for males. In general, males tended to disperse further before being shot (3.8 km) than females (1.6 km). Only 3.8% of all animals were shot at distances larger than 10 km. As most animals (84.6%) were shot inside their natal home range, only a small proportion (15.4%) did actually disperse (shot outside mothers home range), which is 32% of all animals surviving to the age of yearlings. Of those dispersed animals, 25% were females. The low dispersal rate is biased by female philopatry and allows actual dispersal only at very high population densities or in sparsely populated regions. In consideration for the low natural mortality proved by radio-tagged animals, the harvest rate is lower than the net reproduction. We did not detect any sex-biased hunting. The dominating hunting method was single hunt at bait, although drive hunts are highly effective. However, hunting rates on piglets and females were too low for regulating the population.     

Can Ingestion of Lead Shot and Poisons Change Population Trends of Three European Birds: Grey Partridge,Common Buzzard,and Red Kite?

Little is known about the magnitude of the effects of lead shot ingestion alone or combined with poisons (e.g., in bait or seeds/granules containing pesticides) on population size, growth, and extinction of non-waterbird avian species that ingest these substances. We used population models to create example scenarios demonstrating how changes in these parameters might affect three susceptible species: grey partridge (Perdix perdix), common buzzard (Buteo buteo), and red kite (Milvus milvus). We added or subtracted estimates of mortality due to lead shot ingestion (4–16% of mortality, depending on species) and poisons (4–46% of mortality) reported in the UK or France to observed mortality of studied populations after models were calibrated to observed population trends. Observed trends were decreasing for partridge (in continental Europe), stable for buzzard (in Germany), and increasing for red kite (in Wales). Although lead shot ingestion and poison at modeled levels did not change the trend direction for the three species, they reduced population size and slowed population growth. Lead shot ingestion at modeled rates reduced population size of partridges by 10%, and when combined with bait and pesticide poisons, by 18%. For buzzards, decrease in mean population size by lead shot and poisons combined was much smaller (≤ 1%). The red kite population has been recovering; however, modeled lead shot ingestion reduced its annual growth rate from 6.5% to 4%, slowing recovery. If mortality from poisoned baits could be removed, the kite population could potentially increase at a rapid annual rate of 12%. The effects are somewhat higher if ingestion of these substances additionally causes sublethal reproductive impairment. These results have uncertainty but suggest that declining or recovering populations are most sensitive to lead shot or poison ingestion, and removal of poisoned baits can have a positive impact on recovering raptor populations that frequently feed on carrion.     

Nest defense of the red-backed shrike Lanius collurio against five corvid species

We compared the antipredation behavior of the red-backed shrike against five European corvids including the jay, nutcracker, rook, crow, and raven. These species differ in body size and in the proportion of eggs and nestlings in their diets. The jay and nutcracker are the smallest, the rook and crow are middle-sized, and the raven being the largest corvid of all. The jay, crow, and raven are habitual nest predators, whereas the nutcracker and rook are not. The harmless pigeon was presented as a control. We analyzed (1) the number of attacks executed by shrikes against intruder presented close to shrike nests and (2) the distance between the intruder and the shrikes during the trial. The small corvids (the jay and nutcracker) were attacked significantly more intensively than the other, larger, corvids (the rook, crow, and raven) and pigeon control. All three large corvids were attacked as exceptionally as the pigeon. Shrikes approached closer to the small corvids and the pigeon than to the large corvids. These results imply that shrike antipredation strategy is adjusted to intruder size, but not to the level of intruder nest plundering specialization. Shrikes weigh up their ability to chase a given intruder away and avoid pointless aggression against large, undefeatable, intruders. This suggests that shrikes are able to asses not only the dangerousness of the intruder but also the potential advantageousness, or otherwise, of active defense.     

Mortality of lemmings, Lemmus lemmus, at peak density in a mountainous area of Norway

We estimated carcass density and determined cause of death in a peak-density lemming, Lemmus lemmus , population at Finse, Norway. Of 74 recovered carcasses, 80% had subcutaneous haematoma (blood underneath the skin) in the head region, though the skin on the skull most often appeared unharmed. Thirty percent were apparently killed by a mustelid predator, while 51% were probably killed by corvids. Carcass density was 26.6 and 9.4ha^-1 in good and poor lemming habitats, respectively.     

Behavioral olfactory discrimination of mixtures in the spiny lobster (Panulirus argus) based on a habituation paradigm

A habituation paradigm was used to examine behavioral aspectsof discrimination of stimulus quality in olfaction in the spinylobster (Panulirus argus). Magnitude of search response to twoconcentrations of artificial mixtures of crab, oyster, mulletand shrimp and to artificial seawater was measured in five lobstersbefore and immediately after habituation to crab mixture. Habituationto crab mixture was accomplished through 2-min presentationsof 5 ml of alternating concentrations (0.05 and 0.5 mM) of crabmixture stimulus, repeated every 5 min for a total durationof at least 3 h. This procedure resulted in at least a 42% decreasein response to any mixture, but the decrease was greatest forcrab mixture, the habituating stimulus. A habituation index,measured as post-habituation response relative to pre-habituationresponse, was used to evaluate discrimination between crab andeach of the other three mixtures. The habituation index wassignificantly greater for crab (90%) than for oyster (49%) andfor mullet (47%) mixtures. The habituation index for shrimpmixture (65%) was intermediate to these three mixtures. Thus,shrimp mixture is perceived by lobsters as being more similarto crab mixture than is either oyster or mullet mixture. Thesepatterns of discrimination parallel those reported for associativelyconditioned lobsters (Fine-Levy et al., 1987, 1988) and fora population of olfactory receptor cells (Girardot and Derby,1988).     

Spatial and temporal variation in lead levels related to body condition in the Mississippi Valley population of Canada geese

Concern over lead poisoning led to progressive prohibition of toxic shot to harvest waterfowl in the 1980's. Nevertheless, waterfowl remain susceptible to ingestion of lead shot because illegal use continues and spent shot persists in soil and wetland substrates. While mortality due to lead toxicosis has subsided, sublethal effects may still affect survival and reproduction. We measured liver lead levels and body condition in 732 Canada geese (Branta canadensis interior) during July 1984 to April 1989 in southern Illinois (USA), east-central Wisconsin (USA), and northern Ontario (Canada). Although we sampled only individuals that were visibly healthy, 55 of 732 (7.5%) geese had elevated liver lead levels (> 2 ppm). Lead levels of 46 (6.3%) geese indicated subclinical poisoning (2-6 ppm) and 9 (1.2%) geese had lead levels indicative of clinical poisoning (> 6 ppm). A greater proportion of juveniles (14.3%) had elevated lead levels than did adults (6.0%), but there was no difference between genders. Lead levels were highest in autumn and winter in southern Illinois, but were low during nesting and summer, despite legal use of lead shot in northern Ontario during our study. Lead poisoning (> or = 5% of the population) was still evident during all seasons in juveniles, and during autumn and winter in adults, 5 to 10 yr after toxic shot was banned from areas where we collected geese during migration and winter. Elevated lead levels did not affect total body mass, lipid reserves, or mineral levels of geese we collected. Protein levels also were unaffected below 10 ppm, but there was evidence of decline at higher concentrations. Thus, it seems unlikely that lead exposure currently affects survival or reproduction of Mississippi Valley Population (MVP) geese via body condition, although other sublethal effects cannot be discounted.     

Corvids infer the mental states of conspecifics

It is well known that humans represent the mental states of others and use these representations to successfully predict, understand, and manipulate their behaviour. This is an impressive ability. Many comparative psychologists believe that some non-human apes and monkeys attribute mental states to others. But is this ability unique to mammals? In this paper, I review findings from a range of behavioural studies on corvids, including food caching, food recaching and food sharing studies. In order to protect their caches from being pilfered, corvids successfully keep track of observing conspecifics, employ a number of caching and recaching strategies, and exploit environmental factors to reduce the amount of visual and auditory information available to observing conspecifics. When giving food items as gifts, corvids give items for which conspecifics have developed a preference. I argue that the available evidence supports the hypothesis that corvids attribute mental states to conspecifics. I further hypothesize that corvids do so through process-driven simulation and the running of non-verbal multimodal rules accomplished by a class of mental representations called semantic pointers.     

Do Reef Fish Habituate to Diver Presence? Evidence from Two Reef Sites with Contrasting Historical Levels of SCUBA Intensity in the Bay Islands,Honduras

Contact between humans and the marine environment is increasing, but the capacity of communities to adapt to human presence remains largely unknown. The popularization of SCUBA diving has added a new dimension to human impacts in aquatic systems and, although individual-level impacts have been identified, cumulative effects on ecosystem function and community-wide responses are unclear. In principle, habituation may mitigate the consequences of human presence on the biology of an individual and allow the quick resumption of its ecological roles, but this has not been documented in aquatic systems. Here, we investigate the short-term impact of human presence and the long-term habituation potential of reef-fish communities to recreational SCUBA divers by studying symbiotic cleaning interactions on coral reefs with differing levels of historical contact with divers. We show that incidences of human contact result in a smaller decline in ecosystem function and more rapid resumption of baseline services on a reef in Utila, Honduras that has heavy historical levels of SCUBA diver presence, compared to an un-dived reef site in the Cayos Cochinos Marine Protected Area (CCMPA). Nonetheless, despite the generally smaller change in ecosystem function and decades of regular contact with divers, cleaning behavior is suppressed by >50% at Utila when divers are present. We hypothesize that community-wide habituation of reef fish is not fully achievable and may be biologically restricted to only partial habituation. Differential responses to human presence impacts the interpretation and execution of behavioral research where SCUBA is the predominant means of data collection, and provides an important rationale for future research investigating the interplay between human presence, ecosystem function, and community structure on coral reefs.     

Temporal resource partitioning mediates vertebrate coexistence at carcasses: The role of competitive and facilitative interactions

Unravelling how biodiversity is maintained despite species competition for shared resources has been a central question in community ecology, and is gaining relevance amidst the current biodiversity crisis. Yet, we have still a poor understanding of the mechanisms that regulate species coexistence and shape the structure of assemblages in highly competitive environments such as carrion pulsed resources. Here, we study how large vertebrates coexist in scavenger assemblages by adapting their diel activity at large ungulate carcasses in NW Spain. We used camera traps to record vertebrate scavengers consuming 34 carcasses of livestock and hunted wild ungulates, which allowed us to assess also differences regarding carcass origin. To evaluate temporal resource partition among species, we estimated the overlap of diel activity patterns and the mean times of each scavenger at carcasses. We recorded 16 species of scavengers, 7 mammals and 9 birds, and found similar richness at both types of carcasses. Birds and mammals showed contrasting diel activity patterns, with birds using carcasses during daytime (mean= 11:38 h) and mammals mostly at night (23:09 h). The unimodal activity patterns of scavengers showed asynchronous peaks among species. Subordinate species modified their activity patterns at carcasses used by apex species to reduce temporal overlap. Also, diel activity patterns of vultures closely followed those of corvids, suggesting facilitation processes in which corvids would enhance carcass detection by vultures. Two mammal species (12.5%) increased nocturnality at carcasses of hunted ungulates, which could be a response to human disturbance. Our results suggest that both temporal segregation and coupling mediate the coexistence of large vertebrates at carcasses. These mechanisms might lead to richer scavenger assemblages and thereby more efficient ones in driving critical ecosystem functions related to carrion consumption, such as energy and nutrient recycling and biodiversity maintenance.     

Phenotypic variation during cloning procedures: analysis of the growth behavior of clonal cell lines

The production of recombinant protein from mammalian cells is a key feature of the biotechnology industry. However, the generation of recombinant mammalian cell lines is still largely performed on an empirical basis and there are many potential areas for enhancement. We have shown previously that despite two rounds of limiting dilution cloning (LDC) of recombinant cell lines, there remained a high degree of heterogeneity in the resulting cell lines. We suggested that a rapid phenotypic drift occurred with these cells. It was unclear if this was a consequence of the added burden of production of a recombinant protein, the selection procedures, or merely an inherent feature of cell growth in culture. To address this, we have subjected untransfected (parental) cells to three successive rounds of LDC and monitored the growth properties of the resultant cells. The results show that despite repeated rounds of cloning, it was not possible to obtain phenotypically similar cell lines. We also demonstrated that this phenotypic drift is not due to gross changes in the protein p27, a key regulators of the cell cycle. Although cells with a range of growth properties were observed even after three rounds of cloning, the variation in growth patterns between cell lines decreased after cloning. Hence, we suggest that by cloning it may be possible to generate untransfected cells, which have particular growth properties. Starting with a well-defined population of parental cells may aid in the subsequent generation of tranfectants with desired growth properties.     

Thermal Carrying Capacity for a Thermally-Sensitive Species at the Warmest Edge of Its Range

Anthropogenic environmental change is causing unprecedented rates of population extirpation and altering the setting of range limits for many species. Significant population declines may occur however before any reduction in range is observed. Determining and modelling the factors driving population size and trends is consequently critical to predict trajectories of change and future extinction risk. We tracked during 12 years 51 populations of a cold-water fish species (brown trout Salmo trutta) living along a temperature gradient at the warmest thermal edge of its range. We developed a carrying capacity model in which maximum population size is limited by physical habitat conditions and regulated through territoriality. We first tested whether population numbers were driven by carrying capacity dynamics and then targeted on establishing (1) the temperature thresholds beyond which population numbers switch from being physical habitat- to temperature-limited; and (2) the rate at which carrying capacity declines with temperature within limiting thermal ranges. Carrying capacity along with emergent density-dependent responses explained up to 76% of spatio-temporal density variability of juveniles and adults but only 50% of young-of-the-year''s. By contrast, young-of-the-year trout were highly sensitive to thermal conditions, their performance declining with temperature at a higher rate than older life stages, and disruptions being triggered at lower temperature thresholds. Results suggest that limiting temperature effects were progressively stronger with increasing anthropogenic disturbance. There was however a critical threshold, matching the incipient thermal limit for survival, beyond which realized density was always below potential numbers irrespective of disturbance intensity. We additionally found a lower threshold, matching the thermal limit for feeding, beyond which even unaltered populations declined. We predict that most of our study populations may become extinct by 2100, depicting the gloomy fate of thermally-sensitive species occurring at thermal range margins under limited potential for adaptation and dispersal.     

Habitat but not group size or recent predator activity affect corvid collective vigilance at carcasses

Vigilance is an important anti-predator behaviour that can be an indicator of the predation risk faced by potential prey animals. Here, we assess the collective vigilance, or the vigilance level of an entire group, of corvids (Family: Corvidae) at experimentally placed carcasses in a desert environment in Australia. Specifically, we explore the relationship between collective vigilance levels and the habitat in which the carcass was placed, the time since a potential predator (dingo Canis dingo, wedge-tailed eagle Aquila audax or red fox Vulpes vulpes) was present at a carcass, and the group size of corvids around the carcass. We found that corvids are more vigilant in open habitat, but that group size and the recent presence of a potential predator does not affect the collective vigilance behaviour of corvids. The results demonstrate the important link between habitat and vigilance, and that animals may adopt anti-predator behaviours irrespective of the size of the group in which they occur or the recent presence of a potential predator.     

Effective nut dispersal by magpies (<Emphasis Type="Italic">Pica pica</Emphasis> L.) in a Mediterranean agroecosystem

Scatter-hoarding animals such as corvids play a crucial role in the dispersal of nut-producing tree species. This interaction is well known for some corvids, but remains elusive for other species such as the magpie (Pica pica), an abundant corvid in agroecosystems and open landscapes of the Palearctic region. In addition, the establishment of the individual dispersed seeds—a prerequisite for determining seed-dispersal effectiveness—has never before been documented for the interaction between corvids and nut-producing trees. We analyzed walnut dispersal by magpies in an agroecosystem in southern Spain. We used several complementary approaches, including video recording nut removal from feeders, measuring dispersal distance using radio tracking (with radio transmitters placed inside nuts), and monitoring the fate of dispersed nuts to the time of seedling emergence. Magpies were shown to be highly active nut dispersers. The dispersal distance averaged 39.6 ± 4.5 m and ranged from 4.1 to 158.5 m. Some 90% of the removed walnuts were cached later, and most of these (98%) were buried in the soil or hidden under plant material. By the time of seedling emergence, ca. 33% of nuts remained at the caching location. Finally, 12% of the cached nuts germinated and 4% yielded an emerged seedling, facilitating the transition to the next regeneration stage. The results demonstrate for the first time that magpies can be an effective scatter-hoarding disperser of a nut-producing tree species, suggesting that this bird species may play a key role in the regeneration and expansion of broadleaf forests in Eurasia.     

Breeding season diet of the Goshawk Accipiter gentilis in Wales

Information on the diet of the Goshawk Accipiter gentilis during the breeding season was collected in Wales during 1991–1993. Diet consisted mainly of birds (87%) and mammals (13%). Forty-five prey species were collected, ten of which were important in numerical or biomass terms: Feral Pigeon Columba livia , Woodpigeon Columba palumbus , Crow/Rook Corvus coronet Corvus frugilegus , Magpie Pica pica , Jay Garrulus glandarius , Mistle Thrush Turdus viscivorus , Song Thrush Turdus philomelos , Blackbird Turdus merula , Grey Squirrel Sciurus carolinensis and Rabbit Oryctolagus cuniculus . Pigeon biomass was important throughout the breeding season and was more important in the diet of nesting Goshawks on higher ground (>250 m). On lower ground, corvids, mammals and pigeons were the main contributors to the Goshawk diet. Rabbits were more frequently taken at lower nesting territories, and thrushes occurred at all altitudes. Mammals, particularly Grey Squirrel, were found in higher numbers in the diet of Goshawks nesting in small woods (<1000 ha) compared with the diet of Goshawks nesting in two large forests ( c . 3500 ha and c . 6100 ha). Goshawks preyed upon juvenile Woodpigeons, corvids and thrushes, and switched from young thrushes to young corvids as the latter became available. Predation peaks on young birds corresponded with the presence of nestling Goshawks in late May to early July. Predation of juvenile prey led to a decrease in mean prey item mass (April-May, 437 g; July, 376 g). No evidence was found to suggest that sexual size dimorphism in Goshawks resulted in partitioning of prey captured during the breeding season. Differences found were probably due to local abundance and vulnerability of prey species rather than specific selection by the two sexes.     

Pheasant release in Great Britain: long-term and large-scale changes in the survival of a managed bird

The release of artificially reared pheasants is a widespread practice in Great Britain, used to increase the number of birds available for hunting. We examined the spatial and temporal patterns of release and shooting between 1960 and 2014 using data from a self-selected sample of 1195 sites. We examined changes in the efficiency of release, the contribution of birds that were not released that year to the numbers shot, and the form of these relationships through time. An annual estimate of the efficiency by which releasing increased the numbers shot was 50% over the period 1960–1990 declining rapidly to 35% by 2005 and reducing more slowly thereafter. There was no obvious regional pattern to this relationship. It has been hypothesised that the efficiency of releasing is lower on sites that release higher densities of pheasants; this study does not support this hypothesis. Annual variation in the density of birds shot in the absence of releasing (1960–1990) was closely correlated with a measure of annual gamebird chick survival. After this date, the relationship was no longer significant, consistent with a decline in wild pheasant stocks and coinciding with the declines in other farmland birds. We highlight increased fox abundance, genetic and behavioural changes arising from the rearing process, and increased shooting in late winter as possible causes for the observed decline in releasing efficiency. We consider the general increase in rearing, habitat changes, increased disease or losses to protected predators as unlikely to have been important causes of the changes in releasing efficiency. Pheasant releasing results in increased numbers for shooting, but has not prevented the wide-scale decline of wild pheasant numbers.     

Amplification success of multilocus genotypes from feathers found in the field compared with feathers obtained from shot birds

Effective DNA extraction methods from bird feathers have facilitated non‐invasive sampling, leading to the suggestion that feathers are a great source for genetic studies. However, few studies have assessed whether all feathers can be used or provide equal numbers of useful templates. In this study, feathers collected in various ways from Red Grouse Lagopus lagopus were examined to establish the quality of DNA extracted. Individual samples were classified into two categories according to whether they were collected from shot birds or found in the field. DNA was extracted from all samples and genotyped at 19 microsatellite loci. PCR products were analysed on a MegaBACE 1000. A total of 93% of the ‘shot’ category produced a genotype that was considered successful (i.e. 15 of 18 loci) and 23% of the ‘collected’ category produced successful genotypes under the same criteria. There was a significant difference between shot and collected samples in genotyping success and the observed number of missing loci. Recommendations and best practices are discussed along with the utility of bird feathers as a source of DNA for population and conservation biology.