Tuesday, March 2, 2010

February Losses

February started with 32 larvae in hibernation at my main study site. None had been lost during the first 17 days of January but then four went missing during the last 14 days of that month (to assumed predation) and another desiccated and perished.

I can report that eight were lost to assumed bird predation during February and one more to ‘desiccation’. 24 are now extant.

So far this winter, 16 larvae have been lost to apparent predation. It is highly unlikely that any of these have moved position, given the cold weather.

Since mid January the (apparent) predation rate has been running at circa two per week, and may well be increasing. There is a distinct predation hot spot in a central area of the site, from where nine out of 12 hibernating larvae have vanished to assumed predation. This area is alive with flocks of tits, more so than the rest of the wood.

So far this winter 16 larvae have succumbed to apparent bird predation, of which 14 were on buds and two on scars on stems. We have no idea how normal this is as there is no base line data – this is the base line. I need to do comparable studies over several winters. Two have died due to ‘desiccation’, a phenomenon well known to those of us who breed iris.


No comments: