Joah Robert Madden

The release of 10s of millions of common pheasants ( Phasianus colchicus ) across the UK for shooting may pose an ecological risk to native species and sensitive habitats, particularly if the birds move into protected areas (PAs) such as Special Areas of Conservation (SAC), Special Protection Areas (SPA) and Sites of Special Scientific Interest (SSSI). The extent of this ecological risk depends on the abundance of pheasants in these sensitive sites, especially if they are attracted there after the shooting season when game management efforts to retain the birds cease. We used relative pheasant abundance measures derived from British Trust for Ornithology bird atlas data from 3793 2 km tetrads across four English counties (Berkshire, Cornwall, Devon and Hertfordshire) to determine if pheasants preferentially disperse into or reside in areas with greater PA coverage. We analysed relative abundance in both the winter shooting season and the breeding season using a Bayesian occupancy‐abundance model, controlling for habitat type and diversity. Our results showed a strong influence of habitat on pheasant abundance, consistent with known habitat preferences. However, we found no evidence of a relationship between relative pheasant abundance and the proportion of ecologically relevant PA coverage in a tetrad. This lack of a relationship was consistent across all four counties and across both the winter and breeding seasons. Our finding suggests that common pheasants do not preferentially disperse into or reside in protected areas compared to surrounding, unprotected land, suggesting that the ecological impacts caused by released pheasants are no more likely to occur in protected areas than in non‐protected areas.

The release and management of pheasants ( Phasianus colchicus ) in the UK for recreational shooting exerts a range of effects on the ecosystem into which they are released. We studied possible effect of nutrient deposition on epiphytic tree flora at 20 pheasant release sites distributed through England (18) and Wales (2) during winter and spring 2023/24. Sites were all Ancient Semi-natural Woodlands (ASNWs) and had substantial (600-8000 pheasants) in a single release pen. We measured N-sensitive and N-tolerant indicator bryophyte and lichen species on tree trunks near to the pen and then in plots along a transect 100m, 250m, 500m and 1km+ away from the pen. To achieve a gradient of pheasant use, the transects were located in the opposite direction to the game managed / shooting area. We recorded 1.9 times more coverage of N-tolerant lichens and bryophytes combined on selected tree species at the pen-edge compared to the control plots. The relationship showed a decline from the pen edge to 250m away but then stabilised. We also detected higher levels of coverage of N-sensitive tree flora at 100m and 250 m compared to the penedge plot. These measures were also higher at these mid distances compared to the 500m and 1000m plots. We suggest far plots were nearer wood edges and were affected by ambient inputs of aerial N from farmland and other external sources. The overall interpretation is that concentrations of pheasants in and around release pens for several months from late summer until early winter in ASNWs does affect the balance of N-sensitive and tolerant tree flora up to potentially 250m and this is a consideration when locating release pens in and near to sensitive woods.

The release of tens of millions of common pheasants ( Phasianus colchicus ) across the UK for shooting may pose an ecological risk to native species and sensitive habitats, particularly if the birds move into protected areas (PAs) such as Special Areas of Conservation (SAC), Special Protection Areas (SPA), and Sites of Special Scientific Interest (SSSI). The extent of this ecological risk depends on the abundance of pheasants in these sensitive sites, especially if they are attracted there after the shooting season when game management efforts to retain the birds cease. We used relative pheasant abundance measures derived from British Trust for Ornithology bird atlas data from 3793 2km tetrads across four English counties (Berkshire, Cornwall, Devon, and Hertfordshire) to determine if pheasants preferentially disperse into or reside in areas with greater PA coverage. We analysed relative abundance in both the winter shooting season and the breeding season using a Bayesian occupancy-abundance model, controlling for habitat type and diversity. Our results showed a strong influence of habitat on pheasant abundance, consistent with known habitat preferences. However, we found no evidence of a relationship between relative pheasant abundance and the proportion of ecologically relevant PA coverage in a tetrad. This lack of a relationship was consistent across all four counties and across both the winter and breeding seasons. Our finding suggests that common pheasants do not preferentially disperse into or reside in protected areas compared to surrounding, unprotected land, suggesting that the ecological impacts caused by released pheasants are no more likely to occur in protected areas than in non-protected areas.

Large-scale annual releases of pheasants Phasianus colchicus and their subsequent management for recreational shooting create various ecological impacts in the UK. While effects at release sites are fairly well understood, dispersing birds may influence areas farther away. If they enter ecologically important but sensitive protected areas (PAs), any negative impacts could be especially harmful. Using tracking data, from 766 birds across 10 sites, we estimated survival and dispersal of released pheasants and applied these patterns to gamebird release records near English PAs to gauge intrusion risk. Of 2,885 registered release sites, just over half lay within 2 km of a PA. A large number of shoots release relatively few birds while a small number release many birds. Thus, numbers expected to enter a particular PA likely depend both on the size of releases and proximity to the PA. We estimate that, at a national level, a maximum of between 525,000 and 784,000 pheasants might be found within PAs very soon after release, representing around 1.7% of all the pheasants released annually. This number declines over the months after release until in February, we estimate that there are between 131,000 and 196,000 pheasants (0.4% of the total release) might be found within PAs. The critical metric by which ecological damage might occur is their density within PAs. Mean densities soon after release averaged 12.0 birds/ha in PAs within 250 m of release sites. This density declined markedly both in time (as birds died) and space (as they moved further from the pen as potential areas increased). By November, densities in PAs 500-1000m from release sites peaked at 0.5 birds/ha, falling to 0.16 birds/ha in February. These estimated densities are around two orders of magnitude lower than those known to cause strong, lasting impacts within release pens. The results are subject to assumptions about movement behaviour, game management and bias in registration. Despite these constraints, considerable local variation exists, with a minority of high-volume release sites very near PAs posing the greatest potential ecological risk.

In the UK, large numbers of pheasants ( Phasianus colchicus ) are released into woodlands annually for recreational hunting. Post‐release, they are managed to keep them in areas where they can be shot from October to January. At sites with high pheasant densities, they can negatively impact local flora and fauna through predation, trampling, and altering soil nutrients via defecation. The extent of these effects beyond release pen sites is unclear. This study investigated at what distance from release sites a suite of ecological effects of released gamebirds might be detected. We surveyed along 1 km transects from release pens at 20 shoots in Ancient Semi‐Natural Woodlands (ASNW) in England and Wales. We expected higher soil nutrients, fewer characteristic woodland plants, more nitrogen‐tolerant species, more damage to dead wood, and fewer woody seedlings near pens, with effects decreasing with distance. We found that pheasant numbers encountered declined with distance and sites closer to pens had fewer seedlings/saplings, lower vascular plant richness and less decayed wood (although this last result may be an artefact of the study design). These effects did not extend beyond 500 m. Contrary to expectations, soil nutrients, bare ground, and ancient woodland indicator species showed no consistent change with distance, and nitrogen‐loving species and weeds were more common further from pens. We conclude that, in areas beyond release pens in ASNW in lowland England and Wales, where pheasants are not deliberately enticed, any direct negative effects on plant communities, soil nutrients and ground cover do not extend further than 500 m from the point of release. The current licensing of gamebird releases in England aims to protect designated woodlands by controlling releases occurring within a 500 m buffer around protected areas. Our results suggest that this buffer size appears to be appropriate to contain these effects of released gamebirds.

Recent efforts to understand the evolution of cognition have adopted a within-species approach where cognitive performance, and its effects on behaviour, is correlated with fitness benefits and, if related, is assumed to be selected for. We reviewed 45 studies taking this approach, involving 26 species and describing 211 relationships between behavioural measures of cognition and fitness, to explore broader patterns underlying the evolution of cognition. First, we explored patterns in the strength and direction of selection. We found generally weak support for a relationship between cognition and fitness, with >70% of raw published relationships being statistically non-significant, with an even smaller likelihood once co-variates were accounted for. Where significant relationships were found, they were predominantly, but not exclusively, positive, with individuals exhibiting faster learning or more accurate memory also displaying greater (proxy) fitness. Second, we tested how selection might act under different circumstances. A relationship with fitness was more likely when general, rather than specific cognitive entities were considered, and when the fitness measure corresponded to survival rather than reproductive output. Consequently, the study of within-species cognitive evolution remains in its early stages, with evidence that is both incomplete and inconclusive. However, it potentially offers a powerful opportunity to explore the structure of cognition, trade-offs, constraints and the way that it links to behaviours. This article is part of the Theo Murphy meeting issue ‘Selection shapes diverse animal minds’.

Response inhibition (RI), or the stopping of actions, is considered a key component of flexible and adaptive behaviour. Across fields, RI is often treated as a unitary cognitive mechanism. However, we propose that RI consists of a chain of cognitive processes, including the detection of a stimulus, the selection of an appropriate behaviour (go or stop) and the implementation of it (execution or inhibition of a motor response). From this, we propose that individual variation in RI can arise at the early signal detection stage. This idea was tested in a detour barrier task, which is one of the most popular tools to study RI in non-human animals. The role of signal detection in detour tasks has been largely neglected, with a few notable exceptions. We therefore partially replicated two previous studies that manipulated the perceptual characteristics of the barrier, while addressing some conceptual and methodological shortcomings of the original work. Specifically, we compared how detour performance of four bird species (i.e. white leghorn chickens, Japanese quails, herring gulls and domestic canaries) is differently influenced by vertical-bar (VB) and horizontal-bar (HB) barriers. In contrast to the previous work, performance on the detour task did not improve when the perceptual characteristics of the barrier matched the ecological niche of the species. However, all species showed some level of learning, as evidenced by shorter detour latencies (except in herring gulls) and fewer persisting attempts. These findings highlight the need for replication studies and emphasize the importance of improving methodological and conceptual design factors to further investigate the underlying mechanisms of RI in animals. Preregistered Stage 1 protocol: https://osf.io/qvxgh (date of in-principle acceptance: 20/03/2023).

Central place foragers (CPF) are animals that return collected resources to their central place. During foraging trips, individuals may exhibit different strategies and either prioritize energy maximizing (EM) during foraging bouts or minimize the time (Time minimising, TM) they spend away from their central place. The exhibited strategy may depend on the composition and distribution of the desired resources and costs of local threats. Beavers exhibit CPF, collecting timber for food and for use in constructions. We assessed trees felled by beavers and control, unfelled trees at two rivers in England and Norway that differed in resource availability and distribution and history of beaver occupation. We evaluated evidence to support or refute EM and TM strategies. We found that beavers were selective in the size and species of trees that they felled. However, the beavers differed between sites in whether their felling was spatially clustered or more randomly distributed. These results suggest site‐dependent variation in the predictive value of the EM and TM strategies of CPF for beaver material collection behaviors. These differences between the two sites may reflect different optimal foraging strategies driven by different lengths of occupation by beavers in the vicinity.

The soundscape experienced by animals early in life can affect their behaviour later in life. For birds, sounds experienced in the egg can influence how individuals learn to respond to specific calls post-hatching. However, how early acoustic experiences affect subsequent social behaviour remains unknown. Here, we investigate how exposure to maternal ‘cluck’ calls pre-hatching affects the behaviour of domestic chickens ( Gallus gallus domesticus ) at 3–5 days and 17–21 days old. We incubated eggs and played cluck calls to half of them. After hatching, we raised chicks in small groups occupying different enclosures. At 3–5 days old, we tested chicks’ responses to three stimuli: (i) background sound, (ii) chick calls and (iii) cluck calls. We found that the pre-hatching experience of cluck calls reduced the likelihood of moving in response to all three stimuli. At 17–21 days old, some chicks explored beyond their own enclosure and ‘visited’ other groups. Chicks exposed to cluck calls before hatching were three times more likely to enter another group’s enclosure than control chicks, and this was unaffected by the chicks’ social connectedness. Our results indicate age- and context-dependent responses of chicks to pre-hatching cluck-call playbacks, with potential long-term effects on individual social behaviour.