Human activities modify the availability of natural resources for other species, including birds, and may alter the relationships between them. The provision of supplementary food at garden feeding stations, for example, might favour some species over others and change the competitive balance between them. This paper investigates the behavioural responses to competition of the Marsh Tit, a species that is subordinate to both the Blue Tit and the Great Tit.

Urban areas can and do hold significant populations of birds, but we know surprisingly little about how these populations are connected with those present within the wider countryside. It has been suggested that the populations using these different habitats may be linked through seasonal movements, with individuals breeding in rural areas moving into urban sites during the winter months to exploit the supplementary food provided at garden feeding stations. However, little work has been done to test this hypothesis.

Food production and wildlife conservation are often thought of as incompatible goals, and it is rare that conservation studies consider both economics and long-term changes in ecology. However, a decade-long study at a commercial arable farm in Buckinghamshire has found that agri-environment schemes significantly increased local bird and butterfly populations without damaging food production, offering hope for the UK’s farmland birds and butterflies.

Our understanding of the impact of feeding wild birds is far from complete, but we are beginning to unravel the effects of providing foods at garden feeding stations. An important area of research has been to examine how supplementary foods shape populations through its impacts in individuals. Feeding wild birds is a popular pastime and many of us provide seed and other foods to help our feathered friends. But what impact does all this food have? It is a huge resource and one that can increase overwinter survival and bring forward the timing of breeding, but we also know that the feeding of wild birds has been linked to the transmission of disease. Research by Kate Plummer and colleagues provides new insight into one particular aspect of food provision – how it shapes bird populations. Kate’s research has examined the extent to which the provision of supplementary food during the winter months influences the physiological condition of individuals and populations the following breeding season. By using woodland populations of Blue Tits, Kate and fellow researchers have been able to compare the effects of providing fat, and fat plus vitamin E (an antioxidant), against a control population of unfed birds. The feeding carried out during the winter months ended at least a month before the tits began egg-laying. Provisioning with fat and vitamin E was found to alter the composition of Blue Tit populations, such that they included birds that had been in significantly poorer condition prior to feeding. Because those individuals were found to have lower levels of carotenoids in their breast feathers than unfed birds, Kate was able to conclude that supplementing with vitamin E and fat in winter had altered the survival and recruitment prospects of these lower quality individuals; lower levels of carotenoids are indicative of poorer physiological condition. However, provisioning with fat alone was found to have a detrimental impact on breeding birds. It appears that the provision of supplementary foods during the winter months can alter both the structure of the breeding population the following season, and the condition of individual breeding birds. Such effects may have consequences even longer term; through this work, for example, it was found that individuals with higher blood plasma concentrations of malondialdehyde (which is indicative of oxidative damage) produced offspring that were structurally smaller and which suffered from reduced fledging success. The importance of antioxidants, like vitamin E, can also be seen from Kate Plummer’s earlier work on yolk mass. While Plummer et al. (2013) found that winter provisioning with fat subsequently impaired an individual’s ability to acquire, assimilate and/or mobilise key resources for yolk formation, this was not the case where vitamin E was also included in the food presented. A high fat diet, such as that potentially obtained from the food provided at garden feeding stations, may well increase the requirement for antioxidants in order to combat the greater levels of oxidative damage associated with a diet rich in fats. Clearly, there is still much to learn about how the provision of supplementary food affects wild birds and their populations.

The increasing temperatures associated with a changing climate may disrupt ecological systems, including by affecting the timing of key events. If events within different trophic levels are affected in different ways then this can lead to what is known as phenological mismatch. But what is the evidence for trophic mismatch, and are there spatial or temporal patterns within the UK that might point to mismatch as a driver of regional declines in key insect-eating birds? A changing climate is leading to changes in the timing of key ecological events, including the timing of bud burst, the spring peak in leaf-eating caterpillar biomass and the timing of egg-laying in many bird species. If the timings of these different events shift at different rates then there is a danger that they may get out of synch with one another, something that is referred to as phenological mismatch. This may be a particular problem for birds like Blue Tit, Great Tit and Pied Flycatcher, which time their breeding attempts to exploit the spring peak in caterpillar abundance. Much of the recent work on mismatch and its impacts on the fitness and population trends of caterpillar-eating birds has looked at changes over time. However, it is also possible for mismatch to vary in space if species respond differently in different areas, perhaps because of local adaptation to geographic variation in the cues that they use. This paper looks at mismatch in both space and time, using information from three trophic levels, namely trees, caterpillars and caterpillar-eating birds. While information on bud burst came from 10,000 observations of oak first leafing for the period 1998-2016, that for caterpillar biomass was inferred from frass traps set beneath oak trees at sites across the UK for the period 2008-2016. Bird phenology data came from the ‘first egg date’ values calculated from 85,000 nest records of Blue Tit, Great Tit and Pied Flycatcher. The focus of the work was on the relationship between the phenologies of these interacting species; where timing changes more in one species than the other, this is indicative of spatial or temporal variation in the magnitude of mismatch. The results reveal that, for the average latitude (52.63°N) and year, there is a 27.6 day interval between the timing of oak first leaf and peak caterpillar biomass. With increasing latitude, the delay in oak leafing is significantly steeper than that of the caterpillar peak. At 56°N the predicted interval between these two trophic levels drops to 22 days. In the average year and at the average latitude, the first egg dates of Blue Tits and Great Tits were roughly a month earlier than peak caterpillar biomass, meaning that peak demand for hungry chicks occurred soon after the peak in resource availability. Interestingly, peak demand in Pied Flycatchers occurred nearly two weeks later than peak caterpillar availability, suggesting a substantial trophic mismatch between demand and availability for this species within the UK. However, it is worth noting that Pied Flycatchers provision their nestlings with fewer caterpillars and more winged invertebrates compared to the tit species studied, so they may be less dependent on the caterpillar peaks. The work also revealed that the timing of first egg date between years varied by less than the variation seen in timing of the caterpillar resource peak, which gave rise to year-to-year variation in the degree of mismatch. For every 10 day advance in the caterpillar peak, the corresponding advance in the three bird species is 5.0 days (Blue Tit), 5.3 days (Great Tit) and 3.4 days (Pied Flycatcher). In late springs, peak demand from the tits is expected to coincide with the peak resource availability, with flycatcher demand occurring shortly after. In early springs, the peak demand of nestlings of all three species falls substantially later than the peak, leaving the three mismatched. Warmer conditions also shortened the duration of caterpillar peaks. One of the key findings of the work is that in the average year there is little latitudinal variation in the degree of caterpillar-bird mismatch. This means that more negative declines in population trends of certain insectivorous birds in the southern UK, driven by productivity, are unlikely to have been driven by greater mismatch in the south than the north. The lack of evidence for latitudinal variation in mismatch between these bird species and their caterpillar prey suggests that mismatch is unlikely to be the driver of the spatially varying population trends found in these and related species within the UK.

Providing quantitative management guidelines is essential for an effective conservation of forest-dependent animal communities. Traditional forest practices at the stand scale simultaneously alter both physical and floristic features with a negative effect on ecosystem processes. Thus, we tested and proposed a method to define forestry prescriptions taking into account the combined effect of woodland structure and tree species composition on the presence of four bird indicator species (Marsh Tit Poecile palustris, European Nuthatch Sitta europaea, Short-toed Tree-creeper Certhya brachydactyla and Blue Tit Cyanistes caeruleus). The study was carried out in Lombardy (Northern Italy), from 2002 to 2005. By using a stratified cluster sampling design, we recorded Basal Area, one hundred tree trunk diameters at breast height (DBH) and tree species in 160 sampling plots, grouped in 23 sampling areas. In each plot we also performed a bird survey using the point count method. We analyzed data using Multimodel Inference and Model Averaging on Generalized Linear Mixed Models, with species presence/absence as the response variable, sampling area as a random factor and forest covariates as fixed factors. In order to test our method, we compared it with other two traditional approaches, which consider structural and tree floristic variables separately. Model comparison showed that our method performed better than traditional ones, in both the evaluation and validation processes. Based on our main results, in deciduous mixed forest where the exploitation demand is limited, we recommend maintaining at least 65 trees/ha with DBH>45cm. In particular, we advise keeping 70 trees/ha with DBH>50cm in chestnut forests and 300 trees/ha with DBH 20–30cm in oak forests. Conversely, in more exploited oak forests, we advise maintaining at least 670 trees/ha with DBH 15–30cm in chestnut forests and 100 trees/ha with DBH 10–15cm. Providing quantitative management guidelines is essential for an effective conservation of forest-dependent animal communities. Traditional forest practices at the stand scale simultaneously alter both physical and floristic features with a negative effect on ecosystem processes. Thus, we tested and proposed a method to define forestry prescriptions taking into account the combined effect of woodland structure and tree species composition on the presence of four bird indicator species (Marsh Tit Poecile palustris, European Nuthatch Sitta europaea, Short-toed Tree-creeper Certhya brachydactyla and Blue Tit Cyanistes caeruleus). The study was carried out in Lombardy (Northern Italy), from 2002 to 2005. By using a stratified cluster sampling design, we recorded Basal Area, one hundred tree trunk diameters at breast height (DBH) and tree species in 160 sampling plots, grouped in 23 sampling areas. In each plot we also performed a bird survey using the point count method. We analyzed data using Multimodel Inference and Model Averaging on Generalized Linear Mixed Models, with species presence/absence as the response variable, sampling area as a random factor and forest covariates as fixed factors. In order to test our method, we compared it with other two traditional approaches, which consider structural and tree floristic variables separately. Model comparison showed that our method performed better than traditional ones, in both the evaluation and validation processes. Based on our main results, in deciduous mixed forest where the exploitation demand is limited, we recommend maintaining at least 65 trees/ha with DBH>45cm. In particular, we advise keeping 70 trees/ha with DBH>50cm in chestnut forests and 300 trees/ha with DBH 20–30cm in oak forests. Conversely, in more exploited oak forests, we advise maintaining at least 670 trees/ha with DBH 15–30cm in chestnut forests and 100 trees/ha with DBH 10–15cm.