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Know your birdsong
JONO LEADLEY, of the Yorkshire WIldlife Trust, shares the birdsong heard at Askham Bog.
A wintry wander around a monochrome Askham Bog, iced in snow and illuminated in weak, morning sunshine is a joy.
In a recent visit, I was greeted at the gates by Yorkshire Wildlife Trust’s latest ambassadors, a pair of very tame robins. Emboldened by handouts from regular visitors, this pair skipped along the boardwalk handrail hoping for a titbit.
A tiny goldcrest seemed out of place flitting along the wire mesh encircling the meadow, in a desperate attempt to find a hibernating lacewing or spider.
The strident and varying calls of great tits punctuated the quiet wood and a piercing high whistle lead my eye to the jerky ascent of a mouse-like treecreeper.
This tiny brown-streaked bird climbed up the fissured trunk of a large alder tree, probing the nooks for small insects, occasionally flashing a hint of its snow-white belly.
After reaching the summit of the thicker branches, it looked around and then flew rapidly down to the base of a nearby tree, where it began the search again.
A little further along the boardwalk, an explosive ‘pi-choo’ announced the presence of a marsh tit. It is a brown bird, similar in size to a blue tit, but lacking the beautiful colouration. Marsh tits sport white cheeks, a black cap and small black bib, beige underparts and dull brown upperparts.
They are virtually indistinguishable from willow tits and, at Askham Bog, the two species occur side by side. The species are visually so similar that they were not separated until the end of the 19th century.
The marsh tit flitted about low down in the lower branches of a birch by the boardwalk. Its loud ‘pi-choo’ call helped me identify this species easily. Willow tits have a lower-pitched ‘eez-eez-eez’ and, once learnt, these diagnostic calls can help confirm the identity of either species.
Willow tits are in rapid decline in England and are firmly placed on the ‘red list’ of birds of conservation concern. They have become extinct in large areas of the southeast of England and East Anglia and it is likely that this decline will continue and therefore may affect our local birds.
This tragic reduction is thought to be down to a combination of factors including changes in woodland management, the loss or drainage of wet woodland and the dramatic impact of a booming deer population on the under-storey of the woodland where willow tits seek food.
They are also suffering from nest predation by great spotted woodpeckers and grey squirrels, both of which are increasing in numbers.
Willow tits are found across Europe and Asia, but are a northerly species and it may be that more subtle changes are occurring as the climate warms causing them to contract their range north.
The marsh tit moved on and I continued my walk. A little later another ‘brown’ tit flitted across the path. Focusing my binoculars on the active bird, the pale brown wing feather edges forming an obvious pale panel, a larger black bib and whiter cheeks hinted that this could be a willow tit.
Then, a second bird flew in and the first uttered that diagnostic slurred call confirming my suspicions. This is certainly not always the case and a number of suspected willow tits I have seen have called and proved themselves to be marsh tits!
Come spring, Askham Bog will be alive with birdsong and this is a great time to look out for and hear both marsh and willow tits.
Willow tits sing a slightly mournful descending series of ‘pew pew pew’ notes while marsh tits have a variety of songs the most common being a refrain I liken to ‘chipa-chipa-chipa’. Another difference to look out for in spring is that willow tits excavate their own nest hole, unlike all other English tits which use ready-made holes and cavities.
My cold toes reminded me that we are still in the grip of winter and happy with my sightings I completed my loop around the boardwalk. The melancholy, wavering hoot of a tawny owl signalled the approaching dusk so I headed home.