I have come across a flock of Siskins in my street a couple of times this week. Today, about 20 birds were quietly feeding on seeds of a large Italian Alder (Alnus cordata), a widely planted tree along avenues. They were easily disturbed by car door slamming or a passing dog and tweeted while they flew to a higher tree. Given that my photos are quite distant, I decided to draw a male feeding on alder catkins (above).
Siskins - like Waxwings - are nomadic birds that follow unpredictable resources: tree seeds, with conifers, alder and birch being favourites. In the winter, substantial numbers of Scandinavian Siskins join the British breeding population and disperse more widely. In Scotland, Siskins appear in gardens in higher abundance in years with poor spruce cone crops, indicating more nomadic behaviour in these years and search for alternative food sources. Conversely, they barely come into gardens when their conifer seeds are found in abundance. Sitka Spruce, one of the most widely planted comercial conifer in the UK, has good crops every 3-5 years and this seems to be synchronised across large areas. The large plantations of this tree appear to have benefited Crossbills, Coal Tits and Siskins, which feed on the small seed of the tree. According to the BTO, nesting Siskin populations have increased by 77% since 2004 as the trees in plantations reached maturity and started producing seeds. But Siskins have also altered their behaviour outside their nesting grounds, increasingly using garden feeders - especially peanuts and niger seed - on poor crop years. I wonder if Italian Alder planting in streets might also make easier that we come across this lively little bird.
AILSA J. MCKENZIE, STEVE J. PETTY, MIKE P. TOMS, and ROBERT W. FURNESS (2007). Importance of Sitka Spruce Picea sitchensis seed and garden bird-feeders for Siskins Carduelis spinus and Coal Tits Periparus ater Bird Study, 54, 236-247 : 10.1080/00063650709461480