Spotlight on a starling roost
Guest blogger: Starling expert Chris Feare on how the Autumnwatch camera team helped to confirm fascinating roosting behaviour.
Chris with a pair of tame starlings.
Back in the late 1970s, I can't remember exactly when, I spent a long winter night in a Norfolk starling roost. The aim was to discover what roosting starlings got up to during the night and, more importantly, to watch their behaviour when they entered the roost site at dusk and as they departed at dawn...
I emerged frozen to the core, exhausted, and smelling to high heaven. But I did learn that descent into the trees, from the magnificent coordinated wheelings above, was accompanied by frenzied activity. This involved a vast amount of noise and fighting before settling into an uneasy sleep interrupted by frequent minor squabbles.
A resurgence of noise preceded departure. The birds left in a series of well-coordinated exoduses rather than en masse. A notable difference between arrival and departure was that the (possibly half-asleep) birds frequently collided as they left the roost, something never seen during entry into the trees.
Starlings over Aberystwyth pier © Lindsay McCrae
Filming the roosting starlings for Autumnwatch, using the latest photographic technology, cast new light on this wonderful world of nocturnal starling activity.
With infra-red mini-cameras and microphones pre-positioned on the pier's sub-structure, we were able to watch as the birds, some even using the cameras as roost sites, competed for their individual spaces through song, posturing, stabbing with their sharp bills and vicious fighting.
Infra-red imaging showed some of the starlings were even using the minicams to roost.
The resulting scene showed a hierarchy of roost site occupation never seen before in wild starlings.
Immediately beneath the pier's floorboards the steel beams were structured in a way that provided mini-alcoves. Each of these was occupied by two or occasionally three birds, distinguishable by their small pale feather tips as adult starlings, each bird defending when necessary its individual space in these sheltered sites.
Thermal imaging showed the starlings making use of every alcove and crevice under the pier.
Below them, beams more exposed to wind were also occupied, but the heavily spotted plumage of these birds showed that they were youngsters experiencing their first winter. On the lowest beams pale eye-rings indicated that most of the birds here were young females.
At first, these juveniles spaced themselves out just like the adults above but later they seemed to decide that warmth was more important than space. Then, they huddled together in a long line of tightly packed birds, very difference from their elders above in their comparatively luxurious accommodation.
The speckling of the starlings' plumage distinguishes the adults from subdominant juveniles.
The microphones picked up the full range of starling calls: squawks, whistles, rattles and warbles. But we also heard snatches of blackbird, moorhen, tawny owl and curlew, providing evidence that the renowned mimicry used by male starlings on their nest territories is also used within the winter roost.
It was remarkable to see all this behaviour for the first time with such clarity and in such comfort! The set-up of monitors in Aberystwyth pier's rubbish store had the characteristic odour of deep starling guano totally masked by the contents of the bins. But what a pity we did not have these wonderful facilities when we were researching starling roosting behaviour all those years ago!