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Blue-throated
Goldentail
(male)

Weeks One is full and Week Three has only one slot remaining for our annual
Hummingbird Expeditions to Costa Rica.
Week Two
(3-11 Feb 2009)
is filling fast.

Canivet's
Emerald
(male)

RUBY-THROATS OF 2008:
WHERE DID THEY (FINALLY)
COME FROM?

We give up on Ruby-throated Hummingbirds at Hilton Pond Center. No, we're not going to quit feeding, observing, and banding them, but we're about ready to say we will never again make a prediction about how many we'll capture by the end of a given banding season. Why this hesitation? Mostly because 2008 started out as one of our slowest springs ever for banding ruby-throats at the Center and things got even worse, with only SEVEN hummers banded through 30 June. We were almost despondent over this obvious lack of Ruby-throated Hummingbirds and predicted 2008 would end as one of our worst years--a prediction supported by folks from across the Southeast who also reported unusually low numbers of ruby-throats. Eventually, hummingbirds--as they usually do--began to appear during the first week in July but continued showing up at only an average pace until late August. Then the population exploded and we could hardly keep up with all the hummers in our nets and traps. In the end, 2008 turned out to be our BEST year ever, not our worst. So where did all these late summer and early autumn birds (finally) come from?

All text, charts, tables & photos © Hilton Pond Center

Chart 1: Click on chart above to open a larger image in a new browser window

The season started with the arrival of an unbanded adult male on 9 April 2008 (see red line on Chart 1 above), almost two weeks after our early banding record of 27 March 1991; most years we band our first Ruby-throated Hummingbird (RTHU) at Hilton Pond Center on or before 10 April--which happened to be the date of our second banding in 2008. After that progress was excruciatingly slow with NO new birds at all in May and only one returning bird on 30 May. The next new RTHU was on 2 June, and we ended up with only five new birds for that entire month. As Chart 1 shows, things finally began improving in early July, with a substantial number of new birds appearing in mid-September. The final capture occurred on 9 October, a little later than our average late date for the last RTHU of the season--but earlier than our record of 18 October set 'way back in 1986.

All text, charts, tables & photos © Hilton Pond Center

Chart 2: Click on chart above to open a larger image in a new browser window

The spaghetti-like lines on Chart 1 depict how banding progressed through the 2008 hummingbird season, but it's easier to see how successful we were this year by looking at the bar graph in Chart 2 just above. As shown, our previous best year was three years ago (2005) when we banded 226 RTHU. For some reason there was a big drop in 2006 with only 164 hummers captured, but the Hilton Pond population--which includes both breeding birds and spring and fall migrants--rebounded nicely in 2007 to our fourth-best total of 204 birds. This year trumped them all, with 230 RTHU banded--well above our 19-year average of 173.4. (NOTE: This figure does not include six partial field seasons for which we were away from Hilton Pond for significant portions of the summer.)

If we can trust the red trend line on Chart 2 above, Ruby-throated Hummingbirds appear to be on the increase at Hilton Pond Center. We doubt the upward curve is a result of our becoming more experienced at catching hummers, nor does it reflect more hours of trapping and mist netting.

All text, charts, tables & photos © Hilton Pond Center

Among other things of interest about Ruby-throated Hummingbirds returning to Hilton Pond Center in 2008:

• Of the 38 returns (Table 2), 20 had been banded as adult females in a previous year, while just three were adult males. As shown in Table 3, banded adult females are much more likely to return in a later year.
• Eight of our returns were banded as young, hatch-year females, while seven were young males. This was a surprisingly high number of hatch year males that, as shown in Table 3, typically return at a MUCH lower rate than any other age/sex class
• We were quite disappointed in 2008 not to see any of our three "Methuselah birds" from last year, i.e., two RTHU that were sixth-year birds and one that was an incredible after-sixth-year. Our oldest birds in 2008 were nonetheless beyond middle age for a ruby-throat: Two after-fourth-year females that had to have hatched prior to 2005. (Estimates are that 70-80% of all RTHU die before reaching their second year, so our overall 12.2% return rate is pretty good.)
• One of 2008's after-fourth-year females was banded in June 2005 and not seen again until this year, while the other one skipped 2006.

As usual for our end-of season hummingbird report, we've shown you a bunch of numbers. That's about the only way we know to present information summarizing our annual hummer banding results, so we'll end up with the photo below of an adult male Ruby-throated Hummingbird that hung around until mid-October before departing for the Neotropics.

This bird was color-marked with temporary green dye on its breast--a sure sign it was banded at Hilton Pond Center. We color mark so we don't pull the string and re-trap the same hummers over and over again, but we band so we can better understand migration, longevity, and site fidelity. However, neither our banding scheme or our color marking strategy completely answer that question we asked at the beginning of this essay: After such a slow start in 2008, where did all these late summer and early autumn hummers (finally) come from? Although we suspect few were locally produced, the question will go unanswered. This is because we've never caught a Ruby-throated Hummingbird banded elsewhere by someone else--and we're not REALLY giving up on Hilton Pond hummingbirds until we do.

Comments or questions about this week's installment?
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Be sure to scroll down for an account of all
birds banded or recaptured during the period,
plus other nature notes of interest.

Thanks to the following fine folks for recent gifts in support of Hilton Pond Center for Piedmont Natural History and/or Operation RubyThroat: The Hummingbird Project. Your tax-deductible contributions allow us to continue writing, photographing, and sharing "This Week at Hilton Pond." (Please see Support if you'd like to make a gift of your own.)