Jerry Schultz wondered why there are so many more turkey vultures around, and if it had anything to do with more roadkill. For a guy like me, that is a perfect question. I already knew there were more TVs around the Chicago area, but why is a bit trickier.
First the Round Lake man's original note:
I have spent my entire 66 years in the northern burbs and up until 10 years ago had never seen a vulture now I see them on a regular bases flying over my house. What gives more road kill,warmer weather whats up.
My friend Joel Greenberg, a naturalist and birder who does many surveys in the northern suburbs sent this:
There is no question that turkey vultures have increased dramatically as summer residents in this area over the last decade or so. I have thought about this a fair amount and have discussed it with a number of knowledgeable people and I have yet to hear a convincing explanation. The birds were always in WI, MI, and Kankakee country of IN (as well as northern Porter County but not Lake County, according to Ken Brock. He says, further, that they are now frequently observed in Lake County, often seen landing on the beaches). Thus I doubt climate has anything to do with it. Then there is the possibility of increased food supplies. However, I just don't believe there are more dead animals around then there used to be, particularly road kills; and besides, I have never seen one locally on the side of the road feeding on such morsels. So it remains a mystery to me.
And from Alan Anderson of the Chicago Audubon Society:
1) historical: a) from the Cook County Nesting Season Bird Census (I was co-ordinator) from 1985 - 1997 (census took place in June), most years Turkey Vultures were found in 2 to 4 areas of the county (one year 1990 they were seen in 6 areas, and in 1992 in 5 areas). Number of birds ranged from 1 (1986) to 20 (1990) with an average of 4-14 birds total. b) confirmed nesting in the Illinois Breeding Bird Atlas 1985-1991, TV's were only confirmed nesting ONCE near Black Partridge FP (by an employee of the CC FPD). So you can see they were not very common in summer from 1985 through 1997.
2) current status: I tried checking the IOS Meadowlark summer nesting highlights for 2008 nesting season (Vol 18, No. 1, 2009; page 20) but I guess most birders are only posting their reports to IBET or locally and not for the official nesting records. Anyway, I personally submitted observations from 6 locations (Des Plaines and Rosemont - along the DP River; Plum Creek, Poplar Creek, Bode Lake, Midlothian Reservoir), and I also had them at Spring Creek FP. Other reports locally were 16 at Saganashkee Slough by Wes Serafin ... through the nesting season. Via personal info to me, I know that they were also seen over Skokie Lagoons, Bartel Grassland, Crabtree NC/Baker's Lake area and Somme Woods and elsewhere along the Des Plaines River. I know of one report of confirmed nesting this and the past few years (Stephen Packard and Linda Masters personal info - Somme Woods although they don't want the site mentioned) and think I read of another CO on IBET. They are so common in the Palos area right now that they must be nesting there somewhere, and they might be nesting somewhere in NW Cook as you see some there almost every time you're out birding ...
We (CAS and me and others I've asked to help) are just getting started updating/revising our area bird checklist (Birds of the Greater Chicago Area - a Seasonal Checklist copyright 1982, revised 1998, 2003), we listed TV in the summer as "Uncommon" - Possible to be found in small numbers in suitable habitat. I think we might have to upgrade it to the next level now, which would be 'fairly common' - likely to be found in small numbers in suitable habitat, but I'm not positive (depends on rest of committee too).
As to why the TV increase: probably adapting to humans and residential areas, but also since there is so much food available for them around here - via roadkill.
When she worked for Pioneer Press, Sheryl DeVore wrote a series of articles about all the roadkill she was able to find along suburban roads (she did some sort of minimal study and had some other data too), and how much there was. You might be able to access or find those articles in the PP archives.
Anyhow, since there is so much to scavenge on (roadsides and in the FP's), that's probably the main reason TV's have increased. ) I think I've seen more this year than last year too, but that could be due to a bad memory!)