Dijkstra B. 2013. House Martin Delichon urbicum uses horse’s pee to collect nest material. Drentse Vogels 27: . During a dry spel in June 2013, nest-building House Martins were seen to visit a horse pen some 220 m away from the nest, where they collected mud from spots where horses had recently peed, presumably the only moist ground available. The nest also contained horse’s hairs, another reminder where the nest material had been collected. In this particular village, Anderen in northern Drenthe, conventional dairy farming has largely been outplaced, and many small landholders now keep horses and ponies. The local population of House Martins has increased from 14 pairs in 2011 to 57 in 2013.