The Lauriston Farm project is all about change. And, as rewilding of the site proceeds, it is important to scientifically document the precise sequence of living things that appear on the property, especially those not previously living there (not, at least for about a century – that is how long intensive annual sheep grazing has been happening.) Four times every spring, I lead a walk of volunteers to perform a structured bird census on the Farm, and its bordering hedgerows and woodlots. Because identifying birds by song alone is critical for a census, and most volunteers are not familiar with the songs and calls of the species we encounter on these walks, I teach the volunteers all the songs and calls we hear. About two dozen persons participate each spring (the numbers are kept limited to reduce human conversation, so we can hear bird song!).

Bird Survey Method

We use the British Trust for Ornithology (BTO) Breeding Bird Survey methodology. This is designed to optimise the consistency of breeding bird census counts, which are therefore done only in the breeding season (in our case, March to June inclusive) when bird song peaks. However, we also count birds that do not show clear evidence of breeding (not carrying nesting materials, actually nesting, or feeding offspring) on the Farm census, as we are interested in species that visit/fly over the property, perhaps foraging on/over it, and not just the local breeders.

The BTO census methodology relies on transects (parallel straight-line walking routes) about 200 meters apart to cover any area. However, because the entire Farm covers only about 100 acres, of which the centre is fenced off to protect the ground-breeding birds, and one can easily hear any bird over the distance of one-half of the property diameter, the route we take on these census walks is around the perimeter – about two kilometers, following the trail outside the main Farm fence. Since birds sing most in the early morning hours, our walks start “at the crack of dawn”—about 7 am in late March, through to 5:30am in late June.

Census Results

The census results, over the last two years that we have run it, are very encouraging. They show slowly increasing numbers of species, including some that have clearly “recolonized” the central meadow, such as Skylarks. Their hauntingly beautiful song, usually rendered from high in the sky as the males execute their upward spiral and downward “float” display, is now heard every day all spring, over the centre of the Farm; they have rapidly returned to this site, previously made too dangerous for their nests by the trampling of sheep, and running of dogs. Other species which appear to be increasing in numbers are largely found in the hedgerows and woodlots around the edge of the property: Reed Buntings (along the north edge, nearest the Firth of Forth), Whitethroats and Blackcaps (in the copses at the north and west), and, at least temporarily in early 2022, a lone Yellowhammer (which did not appear to stay and breed – but is a keystone species for meadowland.)

Overall, we see and/or hear about 25 different species in March, increasing monthly as the spring migration proceeds, to just over 30 species in late May and June. Of course, many of these are not nesting on the property, merely passing over it or roosting in the fence-line trees and shrubs. Perhaps the least common species encountered over the two years was Grasshopper Warbler, whose longwinded insect-like song was heard in the tall grass right beside the bus route on Silverknowes Road, close to the north end of the property. While this bird is tricky to identify for novices, and often skulks in the grass unseen, it is probably not that rare – just hard to spot.

Identifying Birds Using the Merlin App

A new tool for many of us in birding, invaluable in census work, is Merlin, a mobile phone app which can accurately identify any birdsong or call. It is free to download, having been developed for public use by the Cornell University Laboratory of Ornithology in Ithaca, New York. It uses a massive library of birdsong recordings submitted by observers from many countries, on which its AI software has been “trained”. It is so acoustically sensitive that it can pick up songs and calls too faint for some humans to hear (especially those of us who are older!) Remarkably, after using it many times in many parts of Europe and North America, my estimate of its “false-positive” error rate – i.e. stating a specific species has been heard which is actually not there, due to mistaking another species for it – comes to only a few percent of all the species it identifies. Almost all of these mis-identifications involve call-notes, which are much more similar across species than full territorial songs. Best of all, Merlin is so easy to use that one census walk allows me to teach all the participants to use it on their own phone. To their delight, it means they leave that session fully independent in their ability to identify any bird sounds they hear. As I say to them on parting, “You don’t need me anymore.”

Merlin has created a slight dilemma for census work because it systematically “hears” more species than most observers do at the same time and place – typically an extra 10-15 % of species at the Farm. Therefore, I make note, in the short report I prepare for each census walk, of birds heard “only by Merlin.” Of course, Merlin cannot identify any bird encountered which remains silent – which is typical of birds such as waterfowl on the ponds, or many of those flying over the property, especially before and after the breeding season peaks in April and May. Alertness of observers to these species flying over is required so as not to miss them.

Plans for 2024

In 2024, I will be leading an extra set of census walks, which will be advertised well in advance as to time and date, so that anyone receiving regular emails from the Farm can sign up.

Meanwhile, if you have questions or comments about this article or the census walks themselves, please contact me at john.frank@ed.ac.uk – and I am always delighted to hear reports of unusual species seen at the Farm!