Foraging efficiency of white stork Ciconia ciconia significantly increases in pastures containing cows

Abstract Recent changes in agriculture have had a very strong impact on avian populations, but detailed mechanistic explanations are scarce. Some proposed solutions to avian declines can be complicated because responses are not linear. For example, abandoning pasture management can be detrimental to many open-nesting birds, but also to some others, because livestock perform ecosystem engineering, changing sward height and creating microhabitats for invertebrates, as well as for insectivorous mammals. Both these features affect the foraging efficiency of birds, for example white stork Ciconia ciconia. We studied the foraging activities of storks in the presence and absence of grazing cows, and we show that in extensive farmland in NE Poland, the presence of cows has a highly significant effect on stork foraging efficiency (in our study area mainly catching insects), which may be crucial to improving breeding success. Our results may also be important from a practical point of view. In white stork recovery projects where supplementary food is offered to storks (e.g. chicken and fish provided on feeding platforms) we believe that establishing extensive cattle pastoralism would be better from an ecological as well as from an aesthetical viewpoint.