Tuesday, September 8, 2009

Hummingbirds, shooting for the rufous moon

Ruby Throated Hummingbird, taken through my kitchen window

Chances of discovering a lifer, or even a county lifer in my back yard are getting seriously low nowadays. The Connecticut warbler I had early June might very well be the last lifer I could get while sipping a glass of white wine on my deck.

I was thinking about the next potential target the other day, and suddenly I thought about one possibility. A small, remote but real possibility.

I am talking about the Rufous hummingbird. looking at the Michigan Audubon Record Commitee database, I found the following records :

State Record No. Species (Count) Date County
1 Rufous Hummingbird (1) Oct 9 1974 St. Joseph
2 Rufous Hummingbird (1) Aug 7-11 1988 Houghton
3 Rufous Hummingbird (1) Sep 25-Oct 22 1988 Ogemaw
4 Rufous Hummingbird (1) Oct 8 1997-Jan 12 1998 Mason
5 Rufous Hummingbird (1) Sep 25-Dec 15 1998 Ingham
6 Rufous Hummingbird (1) Aug 16-17 1999 Alpena
7 Rufous Hummingbird (1) Aug 19-Sep 6 1999 Genesee
8 Rufous Hummingbird (1) Oct 25-Nov 20 2000 Berrien
9 Rufous Hummingbird (1) Oct-Dec 5 2000 Ottawa
10 Rufous Hummingbird (1) Oct 4-Nov 2 2001 Van Buren
11 Rufous Hummingbird (1) Oct 26-Dec 31 2001 Oakland
12 Rufous Hummingbird (1) late Aug-Nov 29 2002 Berrien
13 Rufous Hummingbird (1) Aug 15-Dec 26 2003 Calhoun
14 Rufous Hummingbird (1) Sep 14-Nov 8 2003 Ingham
15 Rufous Hummingbird (1) Oct 20-Dec 26 2003 Berrien
16 Rufous Hummingbird (1) Nov 7-Dec 19 2004 Berrien
17 Rufous Hummingbird (1) late Sep/early Oct-Nov 24 2005 Livingston
18 Rufous Hummingbird (1) May 16 2007 Keweenaw
19 Rufous Hummingbird (1) Oct 17-Nov 22 2007 Clinton
20 Rufous Hummingbird (1) mid-Oct-Dec 5 2007 Van Buren
21 Rufous Hummingbird (1) Oct 28-Dec 22 2007 Kalamazoo
22 Rufous Hummingbird (1) Nov 5-11 2007 Berrien
23 Rufous Hummingbird (1) Nov 7-Dec 4 2008 Ottawa
24 Rufous Hummingbird (1) Nov 12-Dec 5 2008 Saginaw

that's 24 record in 34 years, for the whole state. Obviously, I will need a little bit of luck to find one of those little guys feeding at my windows. Having said so, there is a few encouraging facts that makes me think I have a decent chance.

- there is 24 records in 34 years, but 20 in the last 10 years. So that gives about 2 Rufous hummingbirds per year that are supposed to cross the 170 miles long michigan/ohio or indiana border every year. Assuming the attraction radius of my feeder equipped backyard is 100 m, the odds are about 2*100/(170*1609)=0.007%

Ok, that does not seems a lot at first sight.

But I have another point I would like to make.

How many Rufus hummingbirds are out there really? They seem to show up late in the fall, when most birdfeeders are already washed and back to the storage area. So, the 2 birds a year that are reported are actually seen by a few selected birdwatchers that are dedicated enough to keep their feeders free of ice through the fall/winter. How many of these people are they in Michigan? I would bet there is no more than a few dozen of those geeks in my state

Furthermore, 2 birds a year are only the accepted records by the Michigan record committee. I've heard these guys are pretty picky and tend to only accept very well documented records. I'm pretty sure those guys are so picky that most people would not even bother to report a Rufus Hummingbird, specially if they could not take a picture.

That leaves me with only a wild guess to make. I would bet my chances are not 0.007%, but maybe one hundred times higher than that. That's close from 1%.

Call me a fool, but I like my chances. I'll let you know in December.


Jochen said...

How many Rufous Hummers reach Michigan each year?
We'll never know, but I agree that there are far, far, far more than the two reported/accepted each year.
An interesting bit of information is offered by satellite-tracked birds.
Here is an intriguing example I read about recently:
In the year 2008 alone, three satellite-tracked Lesser Spotted Eagles were found to migrate through Switzerland. None of them were observed by local birders in Switzerland, where it is an extreme rarity: The total number of Lesser Spotted Eagles observed in Switzerland in more than 100 years (!) was six = one in 17 years = roughly 2 to 3 in a birder's active lifetime!!!

Even if we presume that the satellite-tracked Lesser Spotteds were the ONLY ones migrating through Switzerland that year (highly, highly unlikely as only a very small fraction of the population had been equipped with satellite transmitters), this would mean that only 2% (if I got the math right) of Lesser Spotted Eagles that migrate through Switzerland are actually seen by observers. The actual number is lilkely to be a lot below the 1% mark.
And we are talking about a big bird of prey here that - when soaring - can be seen from more than a mile away and is really not a difficult bird to observe.
Now, hummingbirds....

Good luck. I reckon it is only a question of time and dedication.

Laurent said...

PResuming that only the satellite tracked eagles migrate through Switzerland is pessimistic.

THe most likely number could be found out if we know the approximate % of satellite tracked eagles versus the whole population, isnt it?

Jochen said...

The rpoblem is that until satellite tracking proved otherwise, common "knowledge" was that all Lesser spotteds, even those breeding in NE Germany (its westernmost outpost) migrated Se towards the Bosporus and Israel. It was only through satellite tracking that we found out a few take the SW route via Gibraltar or Italy. However, we currently do not know what percentage of birds migrate SW and where the 2watershed" is between SW- and SE- migrants. Therefore, a precise population size cannot be calculated.
But I agree that the actual number must be very much higher, possibly tenfold or more.

Jochen said...

Which by the way means there could be as many as a few hundred Rufous Hummers in Michigan each year.