As far as I'm concerned the Stonechat is one of the most complex of species and I'm airing the discovery and photographing of these two birds by Brian Rafferty once more. The more I view the photograph above the more I find it difficult to believe I'm looking at a Stonechat and would never have believed I would witness an event like this.
Stonechats are opportunist feeders and will exploit a wide range of invertebrate species. OK we don't really have to go to Israel for examples of this opportunism but two males were observed in December 1993 in the Neger Desert to prey on and eat a Scorpion estimated at 17mm not including the tail. In the UK birds have been observed hovering over water and picking unidentified prey items off the surface and on one occasion actually dropping into the water. An African Stonechat in Zimbabwe was seen to dive into the water and secure a 3cm Green-headed Bream which it took back to its perch and swallowed whole. There is some evidence of parent birds avoiding some insects such as Ladybirds, a 3 hour observation revealed that none were brought to the young despite the availability of the prey in huge number.
In these two new images of Brian Raffertys observation's the food prey has now been claimed to be Common back-swimmer ruling out the initial suggestion of Great Diving Beetle though you have to view the first two images published here on Birds2blog previously to actually see the prey in the photograph.
The movements of the Stonechat is very complex and too lengthy to discuss here, but to give an insight into the complexities, the species is partially migratory with the majority remaining to winter here on or near their breeding territory, or making lengthy movements within the UK. On a note closer to the recent situation regarding the ice-age conditions, this is the cause of considerable mortality amongst the resident population and I'm due to search Clougha/Birk Bank and shall do so with much apprehension.
I don't want to go too far down this road at the moment but......the hypothesis that there exists a genetic control of partial migration states that the decision about whether a nestling will be migratory or sedentary is already decided in the egg, furthermore, even if both parents are migratory they can produce sedentary young and vice versa, and a single brood can contain both sedentary and migratory nestlings.
Ponder all this next time you see a Stonechat and be amazed......to be continued.
Having looked at the enlarged original pictures I can conform that the invertebrates are in indeed Coxia spp 'back swimming water boatmen'. A much more common species but still interesting in that they are active enough to be needing to be at the surface to breath air. Why? Very interesting...again nature throws up more questions that answers.
ReplyDeletecheers
Dave
Complex little birds these Stonechats.
ReplyDeleteLets hope you find a few on your trek, and I find a few on my patch during migration!
Thanks for the input here which I note with much interest Dave.
ReplyDeleteWill be extremely interested in your Stonechats on passage starting sometime in February but you won't need me to tell you that will you Warren.
Thanks for your continued interest in Birds2blog it is much appreciated.
Pete. You really are enjoying this one and are thoroughly investigating the feeding behaviour of your favourite bird.
ReplyDeleteI hope I have been able to add a little more information to what is already known. I thank you for taking such an interest and making the information and images available to a wider audience.
I know we have probably not heard the end of this one just yet and I look forward to further news from you in due course.
I will publish another entry on my blog soon with more images from my memorable encounter with these wonderful little birds.
A comment with 'feeling' Brian and ready to recognise a remarkable event.
ReplyDeleteI've already been in touch with some people 'at the top' and so far it appears to be a first.
Keep watching!