EUROPA – BIRDS, Swallow / sand martin

Swallow / sand martin The sand martin is not a well-known bird species in Croatia. Its scientifc name, Riparia riparia, means “of the river bank” and it is suggestive of its nesting habitat. The sand martin is a colonial bird species, so many birds nest at the same site. They choose steep riverbanks covered in pebbles or sand and dig horizontal burrows in them at a height where they cannot be reached by the river. These canals can be as much as one metre long and they slant slightly upwards in order to prevent potential flooding. A small chamber at the end of the canal contains a delicatenest made of feathers and twigs. In May and June, the female uses this nest to lay four, fve or six eggs. A sand martin pair can produce two broods a year and it produces the frst within the frst year of its life. Both the male and the female sit on the eggs, switching places over the course of about 16 days. When the chicks hatch, they are fed by both parents. In appearance, the sand martin can be reminiscent of a more well-known bird species: the barn swallow (Hirundo rustica) with which we are more familiar because it is more widely present in our landscape, especially in the Croatian countryside. The sand martin has a similar body shape, but it is smaller. It is between 11 and 12 cm long, its wings and back are brown, while its abdomen is white. A brown stripe is visible on its breast. Its legs are short. Its wings are sharply pointed and its tail is slightly forked. While sand martins are on the wing, their twittering is continuous and they remain “chatty” even as they briefly rest in a roost. The two genders are very similar, which means that it is diffcult to tell males and females apart at frst sight. The sand martin feeds in flight, catching insects. It is a migratory species and winters in Africa, in Sub-Saharan areas and along the east coast, all the way to its southernmost point. It migrates during the daytime. In Croatia, a mass ringing of sand martins was performed in colonies nesting on the River Neretva. The sand martin is present all over Europe and, in Croatia, it can be found near open waterfront areas, as well as in wetlands near the Mura, Drava, Sava, Danube and Neretva Rivers. This bird species is endangered, which means that the number of nesting pairs is decreasing. This is the case across Europe, including Croatia. It has been estimated that nowadays between 6,000 and 8,000 pairs nest in Croatia. The main cause of the decrease in their numbers is the loss of wetland habitats. In 2016, the sand martin was therefore pronounced the bird of the year in Croatia. This was meant to draw the public’s attention to the fact that the species is going extinct in Croatia and encourage responsible individuals in our country to take action in order to prevent its disappearance from the wetlands with which it forms an indivisible ecological whole.