That is a very interesting beak, and there must be an interesting evolutionary story. Is there some sort of flower this bird goes to that requires such a long beak that other birds can't reach?
I'm sure there are many other examples. Does anyone have the expertise to comment on the above. How about other examples using images BPN members have posted?
Scissor-tailed Flycatcher
Roger,
Having spent some time watching the Scissor-tailed Flycatchers "hunt", it is amazing how they use their tail to maneuver. It is unlike most other birds who just drop in on it's prey. These guys can pick bugs out of the air. Usually larger bugs that will change direction when they see birds. The Scissor-tailed Flycatcher just changes directions from a hover or straight flight and eats them.
James
This is a great question Roger. James has covered some aspects but there's more! On road right now so will respond tomorrow. In the meantime, ideas anyone??
OK I promised some info in this. Thanks again to Roger for starting this one.
The long tails of tropicbirds, nightjars, peacocks, wydahs, and some flycatchers etc, the plumes of auklets and birds of paradise, the bowers of bowerbirds, and the like (there are many examples) are considered to be "ornaments". They are often but not always shown by the male of the species. These ornaments are often so extravagant that Charles Darwin was very worried about them because he wondered how they could have evolved through natural selection. He then came upon the idea of sexual selection whereby a trait could evolve just because of "mating advantage" rather than something for example that made you a better forager or nest builder. One explanation for the evolution of these outlandish ornaments is that females are more attracted to males with them than without them and once this mating preference is established, it is advantageous for parents to produce male offspring that have the ornament rather than not. You can imagine that this could get out of control or runaway- females choose males with longer tails and produce offspring with longer tails, which are then chosen by yet more females who prefer to mate with longer tailed males. This runaway process stops when it just becomes too much of an impediment for the male to carry around his ridiculous ornament such that his fitness declines (for example, he becomes easy prey to a predator, or simply can't fly any more, or the ornament costs too much to make).
The above explanation suggests that there is nothing inherently good about long tails or bright head plumes, other than females more often chose to mate with males with these traits. However, another explanation is that these traits actually advertise something about quality of the male as a mate or parent. Therefore females are chosing males with good quality traits, not just that they have long tails. In theory this is open to cheating whereby a male could be of poor quality but still make a bright or big ornament. However, this is where the size or outlandishness of the ornament comes in because it's a lot harder to cheat when you have to build a big ornament compared to a small one.
A third idea is called the "Handicap Principle" whereby a male with a big, brightly coloured ornament is "saying" to potential mates "look at me, I can survive and be successful dragging around this huge, ridiculous tail, so I'm a good choice for a mate". This is a variant on the second idea I mentioned above, but is a little different.
Sexual selection is responsible for a lot of things we see out there including the large size of males compared to females in many species and the fact that males are more often much more brightly coloured than females. The development of this idea is one of Darwin's greatest achievements but is often overlooked because of the huge impact his previous book on the origin of species had on the world. As well, people at the time found it hard to believe that the female of the species could have such a profound influence on the course of evolution! We now know different, don't we boys!
This is a great topic to bring up on the 200th anniversary of Darwin's birth and the 150th anniversary of the publication of the "Origin of Species".
Last edited by John Chardine; 02-24-2009 at 04:04 PM.
For those who may like to learn more about Darwin and the what led him to make his discoveries, here is a book about little known events before Darwin made his famous voyage:
The Man Who Found Time: James Hutton and the Discovery of Earth's Antiquity
by Jack Repcheck.
I started this book a couple of years ago when I was heading into Edinburgh, where the majority of the book takes place. I read most of the book except the last chapter when I had to head to Cambridge. In Cambridge, I opened the book to read the last chapter and found it was set in Cambridge and described the connection to Darwin. It was very interesting being in the places being written about and made the book much more real to me. (That would be a neat hobby: I wish I had the time and resources to read books in the locations where they took place!) It is a very educational book that tells a lot of the conflict between church and science that developed in the early 19th century and it helped me to better understand the controversies that are still prevalent today.
Back to the subject. Does anyone have an explanation for the very long hummingbird beak? Is that an access to a flower type, or another male has a long beak to attract females explanation?
I would think definitely an adaptation to access nectar deep inside flowers Roger. One clue if the trait is for attracting mates is that that male and female of the same species have different length bills. Can anyone think of a species of hummer where this is the case?
Thanks for the book reference. Looks really interesting.
I read an article in my college Evolution class last year about the Purple-throated Carib hummingbird, where the female has a longer bill than the male due to specialized feeding on two different species of Heliconia flowers. The flowers have actually evolved to be different sizes and contain different amounts of energy to depending on the different bill sizes and energy requirements of the male and female. The difference in bill size also allows the females to not have to compete with males for food, and could have evolved as a result of that competition, since I recall that the males were very protective of their flowers.
Unusual bird evolution
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