I produced some sonagrams from the audio and the results were interesting. First up a flight call ( apologies for compressed sonagrams - the files very small and I have scaled them to match others on this blog for comparison. If you click on them they should enlarge):
This looks very much like the Fc's for Magnus' "keep" ( "Wandering") Common Crossbill call, but it sounds a bit 'lispy' or flutely and dare I say sounds like some types I record regularly in Deeside ( though these "look" different on the 'gram). If anyone can let me know how I can upload audio directly on to here please say and I will do it.
Another Newfoundland one:
The one above is similar to Fc2 'over here' in UK, but with features more consistent with Fc1 ( or "British" for Sound Approach readers).
One more flight call from Witbourne, Newfoundland:
Again, very much like the second example. However, this one gives food for thought:
To me this sounded like a toop ( an excitement call): it is lower in frequency than the corresponding flight calls ( as toops are) and has a more "clucky" quality that toops tend to have. Unfortunately the sound clips are small and it is difficult to evaluate the context of the calls to gain a bit more insight. I would still say this one sounds like an excitement call, though I reserve the right to be mistaken here given the brevity of the clip. However, it does seem to closely match the Fc for Type 4 as shown on page 37 of Groth's monograph. Type 4 flight call can be heard HERE. The example Lester sent me, the putative excitement call, sounds nothing like Groth's Fc4, and whilst the bird was in flight ( you can hear the wingbeats on the recording), it is not uncommon for crossbills to elicit excitement calls when flying. The flight calls Lester sent on do not match those for Type 4 either, but equally they do not match the one recording of a putative percna from 1981. If anything they are similar to Type 3. Mixed flocks of types would not be uncommon - certainly they are not over here in the UK. I am no North American Loxia expert but I would imagine Type 3 and 4 are most likely cadidates geographically as they can range from Alaska and British Columbia on the Pacific Northwest right across to Maine and Canada on the Atlantic coast. The fact that they were occuring at the end of the summer suggests a northerly population moving South (and East ?) and that they were feeding on sunflower suggests behaviour of migrating crossbills eg. that they were possibly locally starving with their natural food source depleted - a bit like watching Crossbills feeding on thrift in Shetland ! The fact that Lester photographed some steaked juvenile birds also suggests that this was a post breeding movement. Lester's crossbills may have crossed a considerable landmass to reach Newfoundland ( and the natural barrier of the North Atlantic), or they could have irrupted more 'locally' from nearby Quebec or the Newfoudland mainland. I would imagine there are exciting opportunities to study crossbill movements using stable isotopes given the vast landmass of the USA and Canada.
So if my hunch is correct what Lester had was Type 3 flight calls and what appears to be a different excitement call from those previously described. If I am wrong then the excitement call is indeed a Type 4 flight call variant ( which I don't have access to to verify or compare, that's my excuse anyway). Groth's sonagrams are also displayed in "wide-band" which makes the features more 'blurry' and with a different scale than mine. But what about the fact that for percna there only exists a series of recordings of an individual bird made in 1981 ? Was this a true percna ? Do these crossbills Lester gets every Summer stay on and breed locally in Newfoundland ? Where do they originate from ? Could they be percna ? Is anyone follwing up this rather intriguing case ? If someone can put me up over there I could just about be tempted over to help out - cheap flight to New York and drive up the coast. If only I could get my crossbills over here onto Sunflower seeds, I might just run out of rings ! It would be like catching blue tits on peanut feeders E-A-S-Y ! My first recommendation would be to take feather samples for stable isotope analysis from caught birds and to compare this with historic mueseum specimens from the same region of the USA and Canada.
And just as a final thought prompted from an as always stimulating exchange of emails with Magnus Robb where he referred to the "up till now taboo subject of the potential for New World Crossbills reaching the UK and Europe". Get out with your Telingas folks - more is waiting to be discovered and it might just be you.............
Maybe some for our cross the pond cousins would like to share their thoughts on this ?
