I find this a strange time of year. Last weekend I sat on our veranda in the sunshine with a beer looking down on the belated daffodils. In the woodland I could hear a solitary Chiffchaff’s (Phylloscopus collybita) “Chiff ...chaff...”, the characteristic sound of the first of our ‘summer’ migrants to return to our warming weather. Spring felt well and truly sprung. But today I am back inside with my woolly hat back on, having retreated from the garden by an icy wind. It seems that the weather and nature have become confused; not sure whether to let winter go or to leap into spring. Last week we passed the vernal equinox, marking the point when day and night lengths are equal. Day length sends important messages to much of our wildlife, triggering growth, birdsong and nest building. But the weather does not tie itself so neatly to the trend, oscillating this way and that, challenging the more optimistic wildlife that tries to get ahead of the rest.
The Chiffchaff’s diet is mainly insects. Poor weather will hold back their activity and emergence, making it difficult for their predators to find and dine on them. However it is the male Chiffchaff’s that arrive first and as they are larger than their female counterparts (such physical differences are technically referred to as dimorphism), they are better able to tolerate colder weather with their greater body mass (*). I hope it warms up before the more delicate females arrive and we can soon forget the last gasp of winter’s chill.
*Catry, P., Lecoq, M., Araujo, A., et al. (2005) Differential migration of chiffchaffs Phylloscopus collybita and P ibericus in Europe and Africa. Journal of Avian Biology , 36 (3): 184-190