‘Bars and spots: varying fortunes of our British woodpeckers’, a talk by Dr Ken Smith

The great spotted woodpecker is one of our most rapidly increasing species and has recently colonised Ireland. By contrast, the lesser spotted woodpecker was added to the UK Red List in 2015, its distribution is very patchy and it is too uncommon for the population trend to be monitored by the BBS. In 2010 it was added to the species monitored by the Rare Breeding Birds Panel. In the Netherlands, where there is more young woodland, both the species are increasing and occur in the same areas.

Victorian Avifaunas show that in the late 1890s the lesser spot was the commoner species. Dutch elm disease, transmitted by a bark beetle, led to an increase in both woodpeckers in the 1970s. Following this, the lesser spot started to decline whereas the great spot population stabilised until the 1990s when, coinciding with a crash in the starling population, it started to increase again. Ken and his wife, Linda studied the woodpeckers in their local Hertfordshire oak and hornbeam woodlands. In 1984 there were about 12 great spot nests in 300 hectares of woodland and this rose to about 60 by 2014. A new cavity is excavated each year and out of 1,118 nests, 35% were in dead wood. Out of 123 lesser spot nests 60% were in dead trees and all but two of the remainder were in dead wood on living trees. The great spots forage on dead branches concentrating on dead-wood invertebrates whereas the lesser spots forage on small living branches just using dead wood in the winter.

Recently developed nest inspection cameras on long poles have transformed the study of woodpecker nests. Great spots on average laid 5.3 eggs and produced 3.8 young. The nest-failure rate was very low (48 out of 1219 nests) so productivity was high. They have generally been laying earlier since 1984 with is a significant relationship between the April/May temperature and laying date. Ideally the peak abundance of the winter moth, mottled umber and green oak tortrix caterpillars should coincide with the chicks’ highest demand for food as this results in higher productivity. However the caterpillar peak can vary by up to a month depending on temperature whereas the woodpecker nesting season is less flexible. This poses the question why aren’t the woodpeckers nesting earlier? Ken and Linda undertook an experiment putting out fat blocks in late winter in some territories but not others. The birds with the supplementary food started nesting about five days earlier than the others and their productivity was about twice that of the unfed birds. Ken suggested that the great spots have increased because:

• some take advantage of garden feeders to supplement their food supply;
• they no longer have to compete with starlings for nest holes in woods;
• there is an increasing volume of deadwood on live woodland trees.

Lesser spots feed mainly on aphids when caterpillar supplies run out and Ken would like to see supplementary food given to some pairs to test whether that increases productivity. The impact of ash die back should also be monitored. Great spots are already taking advantage of the larvae of the beetles which transmit the disease and it is possible that lesser spots will also be able to. Summing up, Ken said that habitat and climate change are likely to be the main drivers of the decline of the lesser spot. There is a small population in the oak woodlands on Dartmoor but more records are needed and Ken asked us to report any lesser spots we come across in Devon on http://www.woodpecker-network.org.uk .

We thank Ken for standing in at short notice when it became necessary to switch to a Zoom meeting, and for giving us such an informative and fascinating talk about these two species. I hope that anyone who is lucky enough to see a lesser spot will report it.

Helen Baker