Urban insect populations would need to increase by a factor of at least 2.5 for urban great tits to have same breeding success as those living in forests according to research published in the British Ecological Society’s Journal of Animal Ecology.
Researchers at the University of Pannonia, Hungary and the University of Sheffield, UK found that providing high quality supplementary food to urban great tits, in the form of nutritionally enriched mealworms, can dramatically boost their breeding success.
“Urban nestlings had considerably higher survival chance and gained an extra two grams of body mass when provided with an insect-rich diet, an increase of 15% compared to the weight of chicks that didn’t receive extra food. This is a substantial difference.” said Dr Gábor Seress, lead author of the research.
These beneficial effects of food supplementation were not seen in forest dwelling great tits where high quality nestling food is abundant. Although the free meals were also readily received by forest parents.
Reduced breeding success in urban bird populations is well documented but this study is the first to show that insect-rich supplementary food during nestling development largely mitigates these habitat differences. The findings indicate that food limitation in urban environments plays a crucial role in reducing the breeding success of insect-eating birds.
Access the paper: Seress G, Sándor K, Evans KL, Liker A. Food availability limits avian reproduction in the city: An experimental study on great tits Parus major. J Anim Ecol. 2020;00:1–11. DOI: 10.1111/1365-2656.13211