Glad you enjoyed the video Jon and David. It will always be niche but if you’re interested in understanding/showing the wider context then there can be little better - the technique may have a wider appeal when the subject is an Emperor on territory at the top of an oak tree, or a pupa hidden away half way up a sallow - I’d better get practicing.
The discrepancy in leafing time certainly creates a big gap between larval development initially, but this gap closes somewhat as the late starters complete more of their development in warmer conditions so tend to rattle through the instars in a way the early starters certainly don’t.
Thanks Pauline - you’re right that I should be careful with exact locations. I’ve been experimenting with hidden trail cams to try to pick up predation - would be interesting to catch someone removing the cats! (These are carefully positioned with only the subject in view so shouldn’t impact on the privacy of others using the woods).
Cheers Wurzel and Trevor - like everything else you get your eye in after a while, so much so that I often miss really obvious things sitting right in front of me when looking for cats - different caterpillars of other shapes and sizes sometimes seem to materialise out of thin air after already searching a branch for several minutes and I wonder how I could have been so blind.
Another check up to see how things have progressed over the last week of sunny days but still cold nights:
Firstly I must report that Hollis Brown has begun to feed - anyone familiar with the Ballad of Hollis Brown will appreciate the significance of this!
Unfortunately, however, Rosemary was nowhere to be seen. I searched extensively hoping that she’d been particularly adventurous in her search for the perfect spot to begin feeding but no luck - I have to conclude that she was picked off a day or two shy of achieving winter survival.
All others were still present and the majority are now feeding, so winter survival can now reasonably be calculated.
Obviously 7 out of the Dylan 20 works out at 35% survival. The wider sample suggests 43% but when this is adjusted in an attempt to account for the fact these ‘extras’ are found throughout the winter (and clearly the likelihood of them surviving grows the later you find them), the number comes back down closer to the 35%.
Last year only 5 of the 20 survived, so survival was lower at 25%. The wider sample was considerably bigger last year, but pleasingly the adjusted survival rate matched that of the 20 very closely, so I do have confidence that these figures represent the wider population.
Interestingly the number of winter survivors in my main study area has been very similar in both years - 14 last year, and 13 this. It might be expected, of course, that the overwintering larvae would be predated down to a certain level, so it’s not surprising to see a larger population suffer greater losses (last year), but with winter survival generally being considered a key indicator of the season to come, it is interesting to see how the relationship between population and survival rate plays out at a given site. If I keep recording a very similar number of winter survivors, regardless of starting population, then it would suggest that the population at my site is being limited by available habitat - if you cram more larvae into the same available space then they just get picked off.
Having said that it’s hard to imagine that the 2-300 sallows that I monitor can only support a little over a dozen caterpillars. But then again many are unsuitable with perhaps only 50 offering good egg laying opportunities, and only the handful that offer optimal conditions being heavily favoured year after year.
As I keep saying, I need a good year to see what happens. Presumably in such a year the tolerance for marginal conditions will increase as density of eggs increases, which will in turn lead to reduced winter survival as marginal conditions take their toll. Or maybe females will just leave to seek out suitable habitat further afield. Certainly plenty to think about as I plod on collecting data.
A few photos to finish - X2 swearing at me from a distance (go on, you can find him), Tiny Montgomery doing an excellent job of melting into the flower sepals (if that’s what they are?), X5 rejecting the sepals and waiting for the real thing (when he gave me the ‘V’ I knew I’d outstayed my welcome), and X3 still leading the field as a result of his position on an early leafing tree.
![33FE38F0-0E2A-47ED-B0C7-A25D262F0036.jpeg (3.47 MiB) Viewed 11558 times X2 not pleased to see me](./files/thumb_17917_54ca34ca5e62099e123d5f43c7a5bdd6)
- X2 not pleased to see me
![7FF47EB4-EB17-45F1-95DB-41FDC1F681D7.jpeg (2.45 MiB) Viewed 11558 times Tiny Montgomery](./files/thumb_17917_6212b31b2dfae57f356acd08d3ea9e88)
- Tiny Montgomery
![1BF5AC0D-EF75-4C01-A0BD-452509890073.jpeg (1.15 MiB) Viewed 11558 times X5 pretty pic](./files/thumb_17917_52aa16114f9923c077aa722b4a429259)
- X5 pretty pic
![19AC58A2-337F-425B-9339-0069701C738A.jpeg (2.41 MiB) Viewed 11558 times X5 more interesting pic](./files/thumb_17917_d3ad6ed60ac0b2e104b059fae4ee10fc)
- X5 more interesting pic
![26DD17E4-8ACF-4215-A32D-BD4C98F549DD.jpeg (752.27 KiB) Viewed 11558 times X5 making his feelings known](./files/thumb_17917_0b62714aa637bc26e0a58959bf1337a9)
- X5 making his feelings known
![210D6F16-3D1D-4F06-80DB-F459ADCD56EF.jpeg (2.6 MiB) Viewed 11558 times X3 well ahead](./files/thumb_17917_e041ffb3888ff2778dda60f5aa91f483)
- X3 well ahead