Friday, September 28, 2012

A New Turkey Vulture Migration Route?

For some time now, I have suspected that the numbers of Turkey Vultures migrating through Metchosin and East Sooke Park each Autumn are probably greater than the total breeding population on Vancouver Island. So where are these other Turkey Vultures coming from? We know that some of them are coming from the southern and northern Gulf Islands, and a few migrate across Johnstone Strait onto Northern Vancouver Island. But what about the large breeding population on the Sunshine Coast? Is it is possible that these birds somehow make their way across the Salish Sea onto Vancouver Island somehow? The distance across much of the Salish Sea is even greater than that across Jaun de Fuca Strait, and would seem to be a barrier to any of the migratory raptors that do travel well across water. Some recent observations from Moorecroft Regional Park in Nanoose, has made me wonder if perhaps the Salish Sea isn't the barrier it was previously believed to be.

On September 27th, 2011, we were doing some sea-watching from Vesper Point, in Moorecroft Regional Park. At app. 12:40, a kettle of 14 Turkey Vultures were spotted, fairly high, and north of Gerald Island. These birds were flapping hard, and seemed to be loosing altitude fairly quickly. When they reached Gerald Island, they began soaring again, and quickly gained some altitude, before soaring ashore over First Bay in Moorecroft, and then continuing on towards Nanoose Hill. About 15 minutes later, another kettle of 17 Turkey Vultures appeared app. two kilometres to the northwest, very high up and soaring towards Gerald Island. They also began catching thermals as soon as they reached Gerald Island, and it didn't take them long to reach the Moorecroft shoreline. Interestingly, this kettle also contained a Cooper's Hawk and an American Kestrel. Although I had little time today to perform active monitoring, I did notice three Turkey Vultures soaring ashore from the direction of Gerald Island.

So where are these birds coming from? The total breeding population on Gerald Island this year appeared to be one pair, and the adults and young left the island back in late August and spent several weeks in Moorecroft before going elsewhere. I would imagine that the total breeding population of the two Ballenas Islands is similar, and it is possible that they made their way onto Vancouver Island previously anyway. I can only think of two explanations. These birds are flying directly across from the Sunshine Coast (app. 28 kms) or from Lasqueti Island (app. 10 kms). I would think that direct crossing from the Sunshine Coast is unlikely. It is simply too far. Lasqueti Island is certainly within the range of a migrating Turkey Vulture though. And there are certainly more than 30 pairs of Turkey Vultures nesting on Lasqueti. How do I know this? Because for years I have counted them as they migrated from Lasqueti across to Parksville, usually coming ashore near the Englishman River Estuary, a distance of about 17 kms. The problem is, I see Turkey Vultures migrating across there every year. Why would they suddenly begin migrating in the other direction? 

I am beginning to wonder if the Turkey Vultures we have seen over the past two days are not actually from the Sunshine Coast, and are using Texada Island as a migratory Stepping Stone. Looking at a map, it becomes obvious that if Turkey Vultures do migrate between the Sunshine Coast and Vancouver Island, this is likley the route that thyey take. Using Google Earth, I made the following calculations;

Smuggler Cove (north of Sechelt) to Thormanby Island = 1.5 kms
Thormanby Island to Texada Island = 3.5 kms
Texada Island to West Ballenas Island = 12 kms
West Ballenas to Gerald Island = 3 kms
Gerald Island to Moorecroft Regional Park = 1 km   

All of this seems entirely possible for a migrating Turkey Vulture to accomplish. Now, with only about a week left in the migratory period, I need to do a lot more monitoring to see if this is indeed the case. Exactly the type of mystery that fascinates me.


Unknown said...

On Sunday we saw a small kettle of Turkey Vultures travelling SE over Esquimalt/Victoria West from our home. Getting exciting that they were part of a migration we watched them closely as they soared on by. An hour later, I looked up and there were 4-6 kettles congregating and travelling N towards Saanich Inlet. This group consisted of 250-300 birds that were very spread out. So, perhaps there is more going on than a simple, direct migration. Perhaps rather, travelling, gathering and travelling some more, creating an overall migration. None the less it was friggin' spectacular!
Kate in Victoria

Abu Anka said...

Very interesting. I have no doubt that there are plenty of facets to their migration that we have yet to discover.