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    Research - requests for assistance

    From the North-East Wales Bird Report 2011-2012

    Lesser Spotted Woodpecker and potential habitat in North-East Wales

    Records received by the CBRG in recent years have been declining and they have come from fewer 1km squares. The reason for this decline has not yet been identified. One possibility is that the habitat required by Lesser Spotted Woodpecker has also become less widely available and that the species is being ‘forced’ to retreat to ever smaller pockets of suitable habitat.

    Recently, a means of testing this hypothesis has become available that does not have huge technical requirements. The Land Cover Dataset has been compiled by the Centre for Ecology and Hydrology based on the broad UK Biodiversity Action Plan habitats. These are available for the whole of the UK at several levels, but here, I have examined the dataset available at the 1km level. I was introduced to this dataset by Dr John Wilkinson of Amphibian and Reptile Conservation, whom I met at a recent Welsh Biodiversity Partnership conference in Bangor after his fascinating talk about Great Crested Newts in North-East Wales.

    Firstly, it is necessary to identify the 1km squares in which the species of interest is currently known to occur. To do this, I used the records provided for this bird report (ie records from 2011 and 2012) and 1km squares from tetrads with confirmed breeding in the recently published ‘The Breeding Birds of North Wales’, where identified by the observer. Secondly, it is necessary to extract the habitat data for just those squares. Thirdly, it is necessary to try to identify those habitat variables for which the actual distribution of the species shows relatively limited variation and select all the squares in the area of concern that fall within those variables.

    I initially looked at the ‘broad-leaved woodland’ variable and found that the squares in which the Lesser Spotted Woodpeckers had been seen showed a variation of 2.6%-39.2% of land cover within each square. Selecting just the squares within this range was a very large number, so I then tried all the other variables that had some variation and narrowed down each remaining set of squares. The variables selected and in their order were as follows:

    Order

    Variable

    Range

    1

    Broad-leaved woodland

    2.6 – 39.2

    2

    Average annual rainfall

    2.19 – 3.65

    3

    Mean summer temperature

    13.31 – 14.18

    4

    Improved grassland

    10.6 – 74.3

    5

    Semi-natural rough grassland

    1.6 – 28.8

    6

    Horticultural

    0 – 43.5

    7

    Built up gardens

    0 – 70.4

    8

    Coniferous woodland

    0 – 8.9

    9

    Open water

    0 – 1.6

    10

    Upland

    0 – 2.4

    11

    Mean winter temperature

    3.84 – 5.05

    12

    Altitude

    13 - 210

    It is not immediately clear why habitat variables like ‘improved grassland’ or ‘semi-natural rough grassland’ should be important to Lesser Spotted Woodpeckers. However, by removing large amounts of land outside the scope of the variables listed in the table, above, squares with unsuitable habitat were removed  and greatly narrowed down the number of potential squares within which the species could potentially be found. This suggests that the amounts of these habitat types within the variation listed above are not likely to be an impediment to Lesser Spotted Woodpeckers being present.

    In total, 307 1km squares were identified as being within the parameters of where the species had been recorded in the last couple of years. These squares are shown in pink in the map.

    LS Woodpecker habitat

    Discussion

    It would appear that potential habitat for Lesser Spotted Woodpeckers occurs much more widely than any of our recent records. I think it is highly unlikely that Lesser Spotted Woodpeckers have been overlooked in all of these squares, though for much of the year they do not make themselves immediately obvious so are difficult to study. One problem may be that the habitat details available for each 1km square do not include those that are important for Lesser Spotted Woodpeckers. Another is that the 1km scale is too large and that there are other habitat features that would be difficult to measure at that large scale that are more important. Among habitat factors found to be relevant in Europe are the presence of dead trees, with snags, high tree species diversity and a high density of dead trees and forests largely of softwoods at small distances from lakes or rivers (Charman et al. 2010). Within England, occupied woods has an open structure, at least to a height of 2.4m within a heavily wooded landscape, oak dominated and with a high abundance of dead limbs (Charman et al. 2010).

    It may be that Lesser Spotted Woodpeckers are being identified where they occur but their actual range is severely restricted, but not by habitat factors. One possibility is that they lose their nest sites in competition with other species, probably including Great Spotted Woodpeckers which seem to be expanding their range in North Wales. Another possibility is competition or predation by Grey Squirrels.

    To check if the identified squares are really not suitable, observers would need to visit each of those squares at the start of the breeding season when the woodpeckers are most likely to be drumming or otherwise vocal, essentially in the early part of the breeding season that may be from mid-February to mid-April. The birds would be easier to see when feeding in the canopy at this time of year as there would be no leaves.

     

    Are we all missing seeing Lesser Spotted Woodpeckers? It seems that we need to check if there are more in the squares identified as being of suitable habitat. We are unlikely to be able to check all the 1km squares, but would any readers be willing to target the 1km squares in say, SJ26, to check them in the late winter and early spring for occupancy by this dainty species of woodpecker? If you are so willing, please let me know so that I can coordinate effort between squares rather than everyone go to the same square.

    Ian M Spence

    Reference

    Charman, E.C., Smith, K.W., Gruar, D.J., Dodd, S. & Grice, P.V. 2010. Characteristics of woods used recently and historically by Lesser Spotted Woodpeckers Dendrocopos minor in England. Ibis 152 (3): 543-555.

    Last updated: 27 July 2015

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