Eurasian skylark

Eleven subspecies are recognized:[3]

• A. a. arvensis Linnaeus, 1758 – northern, western and central Europe
• A. a. sierrae Weigold, 1913 – Portugal, central and southern Spain
• A. a. harterti Whitaker, 1904 – north-western Africa
• A. a. cantarella Bonaparte, 1850 – southern Europe from north-eastern Spain to Turkey and the Caucasus
• A. a. armenica Bogdanov, 1879 – south-eastern Turkey to Iran
• A. a. dulcivox Hume, 1872 – south-eastern European Russia and western Siberia to north-western China and south-western Mongolia
• A. a. kiborti Zaliesski, 1917 – southern Siberia, northern and eastern Mongolia and north-eastern China
• A. a. intermedia R. Swinhoe, 1863 – north-central Siberia to north-eastern China and Korea
• A. a. pekinensis Swinhoe, 1863 – north-eastern Siberia, Kamchatka Peninsula and the Kuril Islands
• A. a. lonnbergi Hachisuka, 1926 – northern Sakhalin Island
• A. a. japonica Temminck & Schlegel, 1848 – southern Sakhalin Island, southern Kuril Island, Japan and the Ryukyu Islands: the Japanese skylark

Some authorities recognise the subspecies A. a. scotia Tschusi, 1903 and A. a. guillelmi Witherby, 1921.[8] In the above list scotia is included in the nominate subspecies A. a. arvensis and guillelmi is included in A. a. sierrae.[3]

In the 19th century multiple batches of Eurasian skylarks were released in New Zealand beginning in 1864 in Nelson (in the South Island) and in 1867 in Auckland (in the North Island). The wild population increased rapidly and had spread throughout both the North and South Islands by the 1920s.[13][14]

In Australia the Eurasian skylark was introduced on multiple occasions beginning in 1850.[14] It is now widespread in the southeast of the continent. In New South Wales it mostly occurs south of 33°S. It is widespread throughout Victoria and Tasmania and also occurs in the south-eastern corner of South Australia around Adelaide.[15]

The Eurasian skylark was introduced to the southeastern Hawaiian Islands beginning in 1865. Although once common, it has declined in abundance on Oahu and is no longer found on Kauai. A study published in 1986 found European skylarks remained only on the islands of Hawaii and Maui and estimated a total population of 10,000 individuals.[16][17]

The Eurasian skylark was introduced to Vancouver Island off the west coast of Canada in 1903; additional birds were introduced in 1913.[18] The population grew and by 1962 there were around 1000 individuals.[19] The numbers have subsequently declined due to loss of habitat, and in 2007 there were estimated to be only around 100 individuals spread over four small areas of the Saanich Peninsula.[20][21]

Eurasian skylarks first breed when they are one year of age. Nesting may start in late March or early April. The nest is probably built by the female alone and is a shallow depression in the ground lined with grasses. The clutch is 3 to 5 eggs. The eggs of the nominate subspecies average 23.4 mm × 16.8 mm (0.92 in × 0.66 in) in size and weigh around 3.35 g (0.118 oz). They have a grey-white or greenish background and are covered in brown or olive spots. They are incubated only by the female beginning after the last egg is laid and hatch synchronously after 11 days.[22] The altricial young are cared for by both parents and for the first week are fed almost exclusively on insects.[23] The nestlings fledge after 18 to 20 days but they usually leave the nest after 8 to 10 days. They are independent of their parents after around 25 days. The parents can have up to 4 broods in a season.[22]

The Eurasian skylark walks over the ground searching for food on the soil surface. Its diet consists of insects and plant material such as seeds and young leaves. Unlike a finch (family Fringillidae) it swallows seeds without removing the husk. Insects form an important part of the diet in summer.[24]

Eurasian skylark in the Lake District, England, with two beetles caught in its beak

In the UK, Eurasian skylark numbers have declined since the 1970s, as determined by the Common Bird Census started in the early 1960s by the British Trust for Ornithology. As of 2017, they were estimated to have declined across the UK by 4-10% over the last 10 years, and by 6-28% over the last 22-25 years.[25] The RSPB have shown that this large decline is mainly due to changes in farming practices and only partly due to pesticides. In the past cereals were planted in the spring, grown through the summer and harvested in the early autumn. Cereals are now planted in the autumn, grown through the winter and are harvested in the early summer. The winter grown fields are much too dense in summer for the Eurasian skylark to be able to walk and run between the wheat stems to find its food.

A list of conservation interventions that could impact the species was published by the RSPB.[26] English farmers are now encouraged and paid to maintain and create biodiversity for improving the habitat for Eurasian skylarks. Natural England's Environmental Stewardship Scheme offers 5 and 10-year grants for various beneficial options. For example, there is an option where the farmer can opt to grow a spring cereal instead of a winter one, and leave the stubble untreated with pesticide over the winter. The British Trust for Ornithology likens the stubbles to "giant bird tables" – providing spilt grain and weed seed to foraging birds.[27]