Thank You, Christian, for the well-reasoned (and tactful) post. I agree with you completely. I thought it was worth pointing out that long-distance migrants are generally not able to simply respond to favorable weather conditions and migrate early. Long-distance migration is an incredible feat requiring an enormous suite of complex physiological adaptations (especially for passerines). Long-distance migrants rely on photperiodic (day length) cues, not only to indicate when they should leave their wintering grounds, but also to initiate the physiological/hormonal cascades required to achieve the body conditions required of migration. Furthermore, neotropical migrants have no way of knowing that conditions may be suitable on their breeding grounds when they are thousands of miles away. For these reasons, it is more likely that short-distance migrants are able to respond plastically to conditions on or near their breeding grounds, both because they have more information and because short-distance migration doesn't require the complex "machinery" that long-distance migration does. Adaptation by long-distance migrants to earlier springs will require many generations of positive selection on those earliest-arriving individuals in order to slowly shift their entire migratory program and their responses to photoperiod cues.
I guess the main points are, 1) As Christian pointed out, understanding distribution and status (of which, arrival time is part) is a key to good birding and recognizing what is unexpected and what is not, 2) Most long-distance migrants are not capable of simply getting up and leaving their wintering grounds in response to conditions on the breeding grounds, and 3) Some species are more capable of early arrivals than others. Certainly, the status of migratory birds is always in flux, and we will continue to see changes in the status and distribution of our familiar species. That is part of what makes birding fun and part of what makes it scary these days. As Christian said, extraordinary arrival dates warrant skepticism, but carefully documenting these events will allow us greater insight into how and to what extent species are capable of adapting to accelerating climate change. Final note: Southern Nevada, where I review eBird records, has had a number of record or near-record early migrants this spring including Hammond's and Ash-throated Flycatchers and Wilson's Warblers. Note that these are all short-distance migrants. Enjoy your Spring! Respectfully Carl Lundblad Moscow, ID (often in CO!) On Monday, March 31, 2014 9:42:21 AM UTC-7, Christian Nunes wrote: > > Birders, > > There are many helpful resources out there that address the arrival dates > of certain species in CO. Most notable is the eBird Bar Charts tool ( > http://ebird.org/ebird/GuideMe?cmd=changeLocation). Plug in CO and then > select the "Entire Region" button on the right-hand box and press go. The > histograms that are presented should lay to waste any doubts that > Broad-tailed Hummingbirds are not expected in the state in the last week of > March. In fact, it should be revealed that that is exactly when they show > up, albeit in low numbers. Scroll down a little and look at when > Band-tailed Pigeons occur in the state. Late March is not when the bulk of > the pigeons are around, but it's not terribly abnormal (note that they > occasionally overwinter in CO). > > And then of course there's the reality that birders make errors. I do not > know Gary or Lora Witt, and I am by no means trying to slight them in any > way, but their report of an Empid foraging over the Republican River in > March instantly makes my skeptical side want to ask, "what made you think > it was an Empid rather than an Eastern Phoebe"? One is much more likely. > The only Empid that even has a remote chance of being in the state in March > is the Gray Flycatcher, and for it to be foraging over a river in the > Eastern Plains is unlikely. There is value in understanding the status and > distribution of certain species since people have been studying and > publishing these trends in books, peer-reviewed articles, etc., for 100+ > years. Also, we are often reminded that the human brain is fallible. An > error is more likely, in this case, then an undocumented hypothetical > record. > > This natural skepticism was, I'm sure, applied to Paula's Ash-throated > Flycatcher report. This is not a personal slight, but just the nature of > the beast. Any report of a heard-only Myiarchus flycatcher in March on the > northern Front Range will get a raised eyebrow from me, and probably most > other people in the birding community. This is why reports of such > magnitude require documentation. I don't know what kind of electronics > Paula is lugging around in the field, but if it's a smart phone, then it's > very easy to use the video function to record bird sounds. I use an iPhone > and it's surprisingly capable of recording sounds if the bird is at a > reasonable distance. Of course, if her bird only called a few times and > then was silent, there may not have been time to record it. Given this > result, it was very appropriate for her to get the word out so that others > could try to get on the bird, whatever it was. > > Tact is required by both the observer of a vagrant bird and by those who > are willing to communicate their skepticism. I do hope that I'm utilizing > it here successfully. > > Christian Nunes > Boulder, CO > > > > ------------------------------ > Date: Mon, 31 Mar 2014 09:23:15 -0600 > Subject: [cobirds] Too bad birders can read... > From: [email protected] <javascript:> > To: [email protected] <javascript:> > CC: [email protected] <javascript:> > > The Empid seen over the weekend in NE Colo., my possible flycatcher heard > last week, Bill Kaempfer's Band-tailed Pigeon of a couple of weeks ago, > and Jeff Jones' recent hummer are all examples of early migrants. (and > probably many other birds that are dismissed because "they aren't supposed > to be here yet") > > Because they take field guides too literally, many birders commonly > dismiss "out-of-season" bird reports and totally ignore even what they see > or hear. > > Birds can fly and take advantage of favorable winds and other weather > conditions...and, because they cannot read books that say they should not > be at a certain latitude before a particular date, they can easily appear > "early" if weather is favorable! > > Paula Hansley > Louisville > > -- > You received this message because you are subscribed to the Google Groups > "Colorado Birds" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] <javascript:>. > To post to this group, send email to [email protected] <javascript:> > . > To view this discussion on the web visit > https://groups.google.com/d/msgid/cobirds/CANF-7hocwU0Mita3Tu08BURT5U1L2eeHAdGyiMqwzt2SNm3GKQ%40mail.gmail.com<https://groups.google.com/d/msgid/cobirds/CANF-7hocwU0Mita3Tu08BURT5U1L2eeHAdGyiMqwzt2SNm3GKQ%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. 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