The latest results from the British Trust for Ornithology (BTO) report a poor year for many of our birds, largely due to a cooler and wetter spring than average.
The Constant Effort Site (CES) and Nest Record Scheme (NRS) findings show that breeding success was well below average pretty much across the board thanks to the late spring and early summer weather, with birds either failing to fledge young or fledglings succumbing to the cold, wet conditions after leaving the nest. Of the 24 songbird species monitored by ringers operating Constant Effort Sites, 18 produced significantly fewer young in 2021; be they migrant warblers, tits, thrushes or finches, the outcome was consistently poor.
Sadly, the weather in 2021 proved less than welcoming, with temperatures well below average throughout spring and heavy rainfall in May, a key stage of the breeding season. “Initial signs were promising,” explained Lee Barber, Demographic Surveys Officer at the BTO, “with many ringers noting good numbers of migrant warblers, such as Chiffchaff, Whitethroat and Sedge Warbler, returning and healthy populations of resident species, including Wren and Cetti’s Warbler.”
That proved to be the highlight, however. As predicted in a cold spring, nest recorders observed that many species were late to start nesting in 2021. “Those of you with nest boxes in your garden may have noticed that the Blue and Great Tits using them started to lay a few days later this year.” noted Dave Leech, the Head of the Ringing & Nest Recording Schemes, “Delays were even more pronounced for many migrant birds, including my own study species the Reed Warbler, and Pied Flycatcher, which started to breed almost a week later than the typical date. In some cases a late start can be beneficial, helping birds to track the advancing emergence of their insect prey but that was not to be the case in 2021.”
Fieldwork for all BTO volunteers has clearly been much more challenging during the pandemic and, after a difficult summer in 2020, the return to the countryside in 2021 was hugely appreciated. “Taking part in surveys is really a way of life for many of our volunteers,” explains Lee Barber. “Even a single record of a nest from your garden can be hugely valuable but there are plenty of ringers and nest recorders that devote a large part of their spring and summer to monitoring work, finding that it benefits their well-being and mental health as much as it helps the birds they study.”
Posted On: 16/12/2021