Every few years, bird survey data gathered by thousands of volunteers from across the UK are brought together to provide detailed information on our wild bird populations status in the State of UK Birds report. This report was published at the end of 2020 and we thought you might be interested in a summary of how UK birds of prey are doing.
Buzzards are increasing everywhere apart from in Wales. They top the English list of species successes with a 1070% increase between 1995-2018, and come second for Northern Ireland with an increase of 1305% between 1995-2018!
Red Kites top the list of successes in Wales, with the highest increase in population (413% increase between 1995-2018).
Kestrels appeared on the list of declines in Scotland, with the second highest decline (61%) between 1995-2018.
Across Britain Tawny Owl occupancy dropped to 53% from 65% in 2005 (see below for more information on this).
Hobbies have shown a long term population increase of 568%, which could be in part due to climate change*. However, short term declines of 23% in the past 10 years, suggesting they have passed their recent peak in population size.
*Hobbies may have benefited from milder conditions due to climate change in the past few decades, but may now be suffering from other negative effects, such as a decrease in the abundance of larger invertebrate prey.
Around 19 million pairs of breeding birds have been lost since 1960s! While this number will include some birds of prey, the majority of these lost birds will be passerines and waders, which make up a significant proportion of many predatory birds diets.
Here are a few extracts from the report that are relevant to birds of prey specifically:
“Increases in the number of red kites and white-tailed eagles have resulted from targeted action, such as reintroduction projects, habitat creation and land management supported through agri-environment schemes. It is worth noting, however, that despite these recoveries, most of these species remain dependent on ongoing conservation support and are found at levels far lower than before historic population declines.
Increases in both the long and short term are obvious for most of our birds of prey. A release from historic levels of persecution and the impacts of organochloride pesticides has allowed raptors such as ospreys, peregrines and marsh harriers to recover. However, hen harriers remain a notable exception, with a lack of recovery, and indeed a short-term decline, caused by illegal persecution.”
“Project Owl
During 2018 and 2019, the BTO ran Project Owl, a set of interrelated, UK-wide research and engagement projects focused on owls.
Two of the major projects within Project Owl aimed to better understand the population status and calling behaviour of tawny owls. We chose tawny owls as the primary focus for several reasons: they’re widespread in the UK (although absent from Northern Ireland and some islands); they have distinctive calls and so can be identified even by inexperienced volunteers; and, most importantly, they are thought to be undergoing a decline which has been detected in the daytime Breeding Bird Survey (BBS) that required investigation through a bespoke survey.
Declines in occupancy
The Tawny Owl Point Survey was a survey to determine their presence or absence (occupancy) during autumn 2018. This was compared to past surveys in 1989 and 2005 to investigate changes in occupancy over time.
The survey followed a standardised methodology and was coordinated via the volunteers of the BTO Regional Network. The method involved carrying out multiple, 10-minute-long surveys in a set of pre-selected tetrads. Volunteers typically visited their tetrad twice and recorded the presence or absence of tawny owls during two consecutive 10-minute periods on each visit, although there was some flexibility in the visit structure.
Over 2,120 volunteers took part, with 2,900 tetrads surveyed. It is estimated that there was a 51% probability of hearing a tawny owl in any given survey period, assuming they were present. Taking detectability into account, there is evidence of a significant UK-wide decline in tawny owl occupancy, from an estimated occupancy of around 62% in 1989 and 65% in 2005, to 53% in 2018. Analysis is currently ongoing to identify potential causes.
Tawny owl calling behaviour
The other survey carried out was the Tawny Owl Calling Survey, which was coordinated by the Garden BirdWatch (GBW). By allowing participants, many new to monitoring, to select their own sites, this survey proved highly popular. It ran from 30 September 2018 until 30 March 2019, with over 9,000 1-km squares surveyed.
Despite the unstructured nature of the design, the large dataset can be analysed to investigate changes in tawny owl calling behaviour over the winter, during the night and in relation to a range of environmental factors.
Analyses are still underway but patterns of calling behaviour will help design and interpret future surveys. There is evidence that owl presence is influenced positively by certain types of woodland and negatively by artificial light and urbanisation.”
The State of UK Birds 2020 report was jointly published by the British Trust for Ornithology (BTO), the Royal Society for the Protection of Birds (RSPB) and the Wildfowl and Wetlands Trust (WWT), together with the UK’s statutory nature conservation bodies.
You can find the full report here:
https://www.bto.org/sites/default/files/publications/state-of-uk-birds-2020-report.pdf