Throughout July, we noticed an increasing number of birds spending time in the vicinity of our farm’s slurry store (large open-topped tank above the ground). Consequently I decided to investigate the reason for this.
The birds numerously seen were flocks of starlings, flocks of house sparrows and a couple of our local black-headed gulls (one in particular was seen everyday, which we named Nigel). From the outside of the slurry store, you could see the birds perching on the edge of the tank and at times flying down inside, often to not be seen for a few minutes.
To take a closer look, I climbed up the ladder on the side of the tank to get to the platform which would allow me to look down into the store.
On this platform, you could look all the way to the bottom of the tank, which during July had only a couple of feet of slurry left within it. From the platform I was able to watch the behaviour of the birds without disturbing the birds . Consequently my suspicions about what the birds were doing were soon confirmed.
All the birds spotted, were exploiting the slurry store as a location to find food, such as feeding on fly larvae hatching in the surface of the slurry. All these different bird species had different strategies to feed in this environment. House sparrows would fly down to the bottom of the tank, to pick larvae from the surface of the slurry whilst on the wing. Starlings would perch on the nuts on the inside of the tank’s walls, before flying down to pick off larvae or hunt on the surface of the slurry. Black-headed gulls would use similar tactics, but would often sit on the surface of the slurry where it was most watery and feed at their leisure.
It was very interesting to watch these birds feed, but now into August these birds have moved off to exploit other further food sources.