In this study, we analyze changing patterns of pesticide use in agriculture in Great Britain over the 1990–2016 period, with respect to the risk they pose to birds. The weight of pesticides applied decreased by 51% between 1990 and 2016, but the area treated increased by 63% over the same period. Over this period, there has been considerable turnover in the pesticides used. The European Union (including Great Britain until 2020) has restricted or banned many pesticides for agricultural use, including organophosphates and carbamates. However, new generations of active substances have been introduced, such as the neonicotinoids, some of which have since been banned. In this analysis, we estimate the annual ‘toxic load’ of agricultural pesticide use in Great Britain for birds, measured as the total number of LD50 doses for corn buntings, Emberiza calandra. We have previously performed similar analyses for bees, for which the total toxic load increased six-fold during this period. In contrast, for birds the total toxic load fell by 80.5%, although still correspond to 8.3e+11 corn bunting LD50 doses in 2016. The decrease in toxicity is largely due to declining use of highly toxic organophosphates in recent years. We identify the pesticides in current use that may pose the highest risk to birds, which include a mix of insecticides, herbicides, fungicides, molluscicides, acaricides and plant growth regulators. The insecticide ethoprop was ranked highest in 2016, with a toxic load of 71 billion potential corn bunting kills. Some of the other chemicals presenting a high toxic load, such as the herbicide chlormequat, are not highly toxic to birds (in terms of LD50) but are used in very large quantities. However, it is important to stress that, in reality, only a tiny proportion of pesticides applied will be ingested by birds, and this will vary according to timing and method of application, persistence of the active substance and many other factors. We further note that impacts of pesticides on birds might often be indirect, for example via depleting their food supply, and that sublethal impacts may occur at much lower doses than the LD50, neither of which do we investigate here. Nonetheless, we suggest that this is a useful approach to highlight pesticides that might be worth closer study with regard to possible impacts.

Social complexity may select for socio‐cognitive abilities. The “loose string” task has become a comparative benchmark paradigm for investigating cooperative problem‐solving abilities in many species, thus enhancing our understanding of their evolution. It requires two individuals working together to solve a problem, specifically by pulling the two ends of a string simultaneously to move a reward towards them. A dyad's performance therefore depends on the individuals’ ability to coordinate their pulling action. Many species, including corvids and parrots, have been tested in this paradigm, but most appear insensitive to the exact cooperative nature of the task. We tested another parrot species, blue‐throated macaws, to further our understanding of social cognition in psittacids. Five birds were tested with different partners in a dyadic setting. The study included two control conditions examining the cognitive mechanism underlying their seemingly cooperative behaviour. All birds were able to simultaneously pull the strings, but their performance did not drop when they were denied mutual visual access, and they failed to obtain food when they needed to wait for their partner. Moreover, the parrots decreased their latency to pull with increasing experience. These findings suggest that the birds may have applied an associatively learnt rule, or relied on acoustic cues, rather than coordinating their actions with the partner. This may not necessarily prove a lack of understanding the partner's role, given that their failure to wait in the delay control test might be explained by their poor inhibitory control abilities. Relationship quality (i.e. affiliation and food tolerance) did not influence dyadic success. Future studies are needed in order to disentangle macaws’ potentially limited cooperative abilities from their lack of inhibitory control.

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We determine the exposure of wild birds to pesticides via consumption of fludioxonil-treated winter wheat seeds following autumn drilling. We recorded the density of seeds left on the soil surface, bird density, and consumption of pesticide-treated seed by birds using camera traps. We calculated the dose ingested by each bird species in a single feeding bout and if they ate treated seeds exclusively for 1 day. We extrapolated this for an additional 19 pesticides commonly used as seed treatments, assuming equal consumption rates. All three fields contained grains on the soil surface (mean 7.14 seeds/m2 on sowing day). In total, 1,374 granivorous birds spanning 18 different species were observed in the fields, with 11 species filmed eating the seeds. Fludioxonil appears to pose a low risk to birds, with <1.14% of the LD50 potentially ingested by a bird for a daily maximum amount of seeds. Analysis of the further 19 pesticides commonly used as seed dressings suggests that the neonicotinoid insecticides imidacloprid, clothianidin, and thiamethoxam represent the highest risk for granivorous birds. For example, chaffinch (Fringilla coelebs) could consume 63% of LD50 of imidacloprid in a single feeding bout, and 370% in a day. Further investigation is clearly required to determine whether seeds treated with these other pesticides are consumed as readily as those treated with fludioxonil, as if so this is likely to cause significant harm.