I was away this week for my RSPB dayjob, which required me staying overnight right in the heart of an English city centre. I arrived at my sixth-floor, identikit motel room just as dusk was falling and looked out at the neon-lit slick of concrete, glass and tarmac laid out before me, with its soundtrack of car engines and police sirens.

However, across the way on a bare concrete rooftop I noticed some fluttering movements, the silhouettes of little birds leaping up and twirling around each other.

I had a good feeling I knew what these birds would be, clearly at home right here in an otherwise lifeless landscape, so I headed out to check my hunch and see what had attracted them to that particular spot.

As I got closer, I could see the birds were spiralling down into two intertwined, forlorn-looking evergreen bushes – a Mahonia and an Eleagnus – sandwiched between a bus stop and an office block. About 10-foot high and a little more wide and showing the signs of having been hacked back at some stage recently, the bushes could hardly be described as attractive or loved but nevertheless were the one little island of life in this desert. Here they are:

And down came the birds, and more of them, and yet more. I saw maybe a hundred descend, but it is quite possible a hundred more were already huddled within the dense twiggy cover. I don’t know if you have guessed but the occupants were Pied Wagtails, coming into roost. Here are just some of the throng - see how many you can spot here (*answer at the foot of the blog).

It is such a fascinating little bird, one that you could definitely describe as having urban tendencies and yet not one that makes it into too many back gardens. By day, their preferred hangouts are car parks, flat roofs and football pitches, anywhere with flat open expanses with either no vegetation or very short and sparse grass where they can dart after insects and pick up any little food morsel on the ground, pumping their overlong tails as they go. This might be how you normally see them:

They then need to find somewhere safe to spend the night, and gathering in the heart of the city means there is much less risk of predators – aerial or ground. In addition, they can take full advantage of the urban heat-island effect, with temperatures in the city centre often two or three degrees above that in the countryside.

The wagtails in this roost jostled a little, with late-comers hovering for a few seconds to find an available perch for the night. Newcomers were greeted with volleys of little clicking noises, which is as they snap their beaks at each other. However, once in, they settled calmly to preen before hunching up to sleep. I could smell the waft of wagtail guano to add to the city aromas.

It just shows that even little things in the urban environment can help wildlife. Every extra bush or tree or flower bed might provide a home for some quite surprising residents. 

* I can definitely see six Pied Wagtails in the photo, but there may be more!