Habitat survey of the Skylark (Alauda arvensis L.) and Crested Lark (Galerida cristata L.) in oilseed rape fields of Golestan, Mazandaran and Ardebil provinces

Birds, in particular larks are damaging to oilseed rape leaves (in autumn and winter seasons). In the present research, oilseed rape fields were visited after growing leaves in line transects along their longest diagonals in Golestan, Mazandaran and Ardebil (Moghan) provinces and the following factors were registered: land size are (hectare), cultivation of adjacent fields, existence of trees, bird species and their numbers. When reaching a damage patch (at least 5% 10% of oilseed rape plants had bird damage signs), first geographic position in the farm, distance to the farm's edge and centre, distance tom hedge, river/stream/canal and road were noted and the following characteristics were measured in a 11ýÃ m plot: number of oilseed rape plants, number of oilseed rape plants having bird damage signs, height of oilseed rape plants (considering leaves), height of oilseed rape stems, number of broad-leave plants, crown cover (%) of oilseed rape plants and number of lark faeces. According to the results, bird damage rate in 129 damage patches was averaged at 46.43% 1.87 that the highest bird damage rate was found in Golestan province (52.82% 2.39). According to statistical analyses, bird damage rate was significantly different among the three regions, damage rate of different bird species in Golestan and Mazandaran provinces, position of bird damage patch, and also between number of oilseed rape plants in bird damage patch and adjacent plots (P0.05). Bird damage rate had positive significant correlation with number of lark faeces and distance to road but negative significant correlation with number (per plot), height (considering leaves) and crown cover of oilseed rape plants (P0.05). There was not found any significant relationship between the remaining factors with bird damage rates (P0.05). According to the results obtained, in order to reduce bird damage rate, it is recommended to: using higher seed/plant density (to 100 per sq m) in where there is bird damage, sowing oilseed rape in early autumn and before the arrival of migrating Eurasian Skylarks, removing broad-leave weeds after an appropriate growth of oilseed rape plants, cultivation of oilseed rape and wheat farms very close together, and cultivation of oilseed rape near roads. :