Are large fields of autumn wheat at Kvismaren, central Sweden, used as nesting and food search habitats by Skylarks Alauda arvensis?

The skylark Alauda arvensis population has declined in Sweden. The breeding in silage fields fails and the success in autumn crops is disputed. Therefore, I decided to study the skylark utilisation of autumn crop fields in Kvismaren, central Sweden. The largest accessible field was selected (40 ha) to get as tough conditions as possible for foraging. I could conclude that the nests were evenly placed, the youngsters developed normally and the occupancy was about 80 pairs or territories per km2. The skylarks searched for food as much inside as outside the large breeding field. The flight distances were on average 204 m and up to 550 m. The conclusion was that autumn crops are probably as good as spring crops regarding breeding habitat; potentially even better as the offspring fledged at least 1‒2 weeks earlier. One potential positive factor for the breeding was the occurrence of unsown tractor tracks (tramlines, 2.5% of the area) which were frequently utilised by the skylarks. Such tracks are commonly created nowadays in Sweden and may replace otherwise desired skylark plots. Jan Sondell, Rulleuddsvägen 10, S-178 51 Ekerö. E-mail: jan.sondell@telia.com Received 15 November 2016, Accepted 26 July 2017, Editor: Robert Ekblom 2000). The index went up from 0.6 at 1 million hectares spring crops to 1.3 at 2.5 million hectares. This striking correlation has put focus on negative consequences when autumn crops replace spring crops. A possible method to improve the habitat for skylarks is to leave small unsown areas in the field (so-called skylark plots), normally two per hectare with an area of 16‒24 m2 (RSBP Leaflet: Skylark plots). Morris et al. (2004) showed that two undrilled plots of 24 m2 per hectare were not related to the skylarks’ nesting success at the beginning of the breeding season: he found 1.27 fledged nestlings without plots vs. 1.31 with plots. Later in the season, when the crop had grown high, the effect of the plots was significantly positive; the number of nestlings was 0.87 per nesting attempt in areas without plots compared to 1.86 in areas with plots. In Sweden Hiron et al. (2012) found that skylarks utilised autumn crops as breeding habitat as much as spring crops, and Berg & Kvarnbäck (2011) found no difference in population density in organic autumn crops with and without skylark plots.