By Russell Wynn, 12 March 2016
For some time now I have been intrigued to know the final destination of the large numbers of Jackdaws that head south over my Brockenhurst garden on winter afternoons. Jackdaws are intelligent birds that can adapt to urbanisation, and as a result their numbers in England have more than doubled in the last 50 years. In winter, hundreds of Jackdaws can be found congregating in communal roosts with other crows, but data on roosts within the New Forest area appear to be limited. So on 18 Dec I cycled south in pursuit of several Jackdaw flocks as they passed overhead, and managed to identify a pre-roost site on farmland just south of the village of Pilley. In the subsequent weeks I worked away at this mini-project, with the aim of identifying 1) the origin of birds using the pre-roost, 2) where they ultimately roosted, and 3) the number of birds involved.
On Christmas Eve the clear conditions encouraged me try and secure some photos of this pre-roost gathering, and work towards identifying the final roost site. I arrived at the pre-roost an hour before sunset, and tucked in behind a pile of silage bales that provided convenient shelter from the cool westerly breeze. There were already good numbers of crows feeding on the nearby grass and stubble fields, together with a sizable flock of Starlings (which later headed southwest towards Lymington Reedbed where there is a know Starling roost). Most of the crows were Jackdaws, but there were also good numbers of Rooks and a few Carrion Crows. A male Sparrowhawk flashed across the fields, briefly scattering the crows and Starlings like black confetti, and a brown Merlin bolted southwest over the distant treetops.
By sunset the flow of arriving Jackdaws had decreased to a trickle, and soon afterwards a glowing full moon appeared over the horizon. This was a prompt for the Jackdaws (now numbering in excess of 500 birds), to transfer to the top of a gnarly old oak tree, where they bickered and chattered in the fading light. The combination of tree, birds and moon provided some nice photo opportunities, and I quickly manoeuvred myself to ensure all three elements were in alignment.
At 1630 hrs, some 25 minutes after sunset and in near darkness, the congregation suddenly erupted from the trees and headed low south across the fields and out of sight. A quick perusal of the map revealed a couple of likely roost sites in that direction, giving me something to aim for on my next scouting mission.
My first attempt to pin down the roost a few days later was fruitless, as I was unable to find a viewing spot to see where the birds were dropping in. But I got enough glimpses over and through hedgerows to ascertain that Walhampton Wood (just east of Lymington) was the likely spot. My second attempt was more successful as I positioned myself on the bridleway running along the southern edge of Walhampton Golf Course, with a clear view over the wood. As darkness approached a gathering of more than 50 Carrion Crows in adjacent trees provided encouragement, and a few bands of Rooks soon joined them. But where were the Jackdaws? Well, it was almost fully dark when they arrived, and I heard them long before I saw them. A great swirling mass of birds arrived from the north and, to my surprise, instead of pitching straight into the wood, they alighted on the golf course and proceeded to feed and wander about. By this stage I could barely make out their dark forms in the gloom, so when they eventually arose as a chattering black cloud and plunged into the wood I had no chance of getting a sensible count.
On 10 January I decided to try and get a better idea of the numbers involved by counting birds moving south towards the pre-roost. My observations up to that point had revealed that the pre-roost and main roost were fed by birds arriving from the north, and this was consistent with my earlier observations of large numbers passing south over my garden at the southern edge of Brockenhurst. I therefore chose to watch from Setley Plain, between Brockenhurst and Lymington, at an elevated watchpoint with a good all-round view. Between 1600 and 1630 hrs I counted 680 Jackdaws heading south, but the southerly breeze meant the flocks kept low and a few were missed or only partly counted (although a Raven and a Goshawk passing overhead provided some compensation). So the next evening, in clearer conditions with birds moving high overhead, I had another go and this time got a more accurate count of 1000 Jackdaws heading south in the period 30 minutes before sunset.
So in summary, with a bit of detective work and some nifty cycling along country lanes, I had pinned down the pre-roost near Pilley, the main roost in Walhampton Wood, and ascertained that at least 1000 Jackdaws were commuting over 5 km from the Brockenhurst area to use this roost site. Why bother flying that distance twice a day when there are plenty of apparently suitable woods around Brockenhurst? My theory is that the slightly elevated temperature near to the Solent coast (and the town of Lymington) means the Jackdaws roosting in Walhampton Wood use less energy overnight keeping warm, so there is a net energetic benefit in commuting. This is especially important during the winter months, which is when communal roosting occurs.
What is also clear from discussion with other New Forest fieldworkers is that other roosts are likely scattered around the fringes of the forest, presumably servicing other Jackdaw winter hotspots such as Burley, Beaulieu and Lyndhurst. However, we have very little information on the exact locations of these roosts or the total number of birds involved. So if anyone has information on these roosts, or is up for the challenge of trying to find one, please let us know!
A fascinating BBC Radio 4 programme on Jackdaw roosts can be found at the link below: