Blog post by Will Kirby, Conservation Scientist, RSPB Centre for Conservation Science.
Breeding hawfinches in Britain have declined dramatically in recent decades.
The last Bird Atlas (Balmer et al. 2013), recorded a 76% reduction in the number of occupied 10km squares.
They are now largely restricted to a small number of core areas in highly wooded regions of England and Wales such as The Forest of Dean and The New Forest. Current estimates suggest that less than one thousand breeding pairs remain.
The RSPB Centre for Conservation Science has been investigating possible causes of hawfinch declines for several years now and our second peer reviewed scientific article from the project: Nest survival, causes of failure and productivity of British Hawfinches Coccothraustes coccothraustes (Kirby et al. 2018) has just been published in the journal Bird Study.
Latest findings
A key finding highlighted in this article is that in our two study areas (Wye Valley and Dolgellau, north Wales), nest survival and productivity appear sufficient to maintain the current populations. This points future research in the direction of other possible causes.
Climbing a tree to install a nest camera
Our next plan is to investigate late winter resource availability by tracking birds between foraging sites in conjunction with a PhD study that is investigating year-round diet through genetic analysis of droppings.
Tough to study?
Hawfinches are difficult birds to study for a number of reasons, not least because there are not many of them left!
They spend most of their time in the woodland canopy, have a very insignificant song, are not particularly territorial and their nests are usually sited high up and extremely difficult to access (average nest height was 16m).
However, by catching birds at their feeding sites and fitting them with miniature radio-transmitters, we were able to track females back to their nests and subsequently monitor them and in some cases fit nest cameras to investigate what predators may be targeting them.
A radio transmitter weighing 0.65g used to track hawfinches
Evidence from the cameras showed that jays were the most frequent nest predator, as has also been found in studies of hawfinches abroad and other woodland species in the UK. Perhaps surprising to some, we recorded no evidence of predation by grey squirrels despite them being numerous in both our study areas.
Our research, supported by camera studies on other woodland nesting species strongly suggests that despite their bad reputation, grey squirrels are not serious nest predators.
Jay predating a hawfinch nest
What’s next?
We’ll keep you up to date as we continue to research hawfinch declines.
This work is funded by Natural England through its Action for Birds in England (AFBiE) programme. The work wouldn’t be possible without the input from many other individuals and organisations that provide access to woods and help with fieldwork.
good work guys!