ADVERTISEMENT
  About the SA Blog Network













Tetrapod Zoology

Tetrapod Zoology


Amphibians, reptiles, birds and mammals - living and extinct
Tetrapod Zoology Home

Three remarkable hummingbird discoveries

The views expressed are those of the author and are not necessarily those of Scientific American.


Email   PrintPrint



Hummingbird assortment, from Haeckel's 1904 _Kunstformen der Natur_. From wikipedia.

ResearchBlogging.org

Hummingbirds are among the weirdest birds of them all. You already have a rough idea of how weird they are – there’s that hovering and humming, oh, and nectar-eating (or nectarivory). But there are a number of facets of hummingbird biology and diversity that aren’t so well known, and in the interests of enlightening you, here are just three of them. I was originally going to write a lot more but I decided to be lazy and spread things out over as many articles as possible. And there’s certainly no shortage of things to talk about as goes the weirdness of hummingbirds.

As usual I’ll start by apologising to the knowledgeable types for whom these supposed revelations are old hat – I have a great dislike of being presented with “did you know?” facts that I arrogantly regard as common knowledge. Anyway, here we go.

– Hummingbirds have to supplement their diet of nectar, since they’d otherwise suffer from deficiencies. There’s no protein in nectar, so hummingbirds have to catch and eat arthropods (more on that below). Nectar is also low in such elements as calcium, and birds famously need lots of calcium, especially females during times of egg production. The females of most birds store calcium in a special tissue known as medullary bone, but hummingbirds are known to have particularly small amounts of this tissue (Adam & des Lauriers 1998), perhaps because their low calcium budget makes it difficult to accrue and maintain. So, what to do? It seems that hummingbirds (egg-producing females in particular) obtain their calcium requirements by eating all kinds of mineral-rich materials including soil, sand and fine grit particles, mineral dust and wood ash (e.g., Verbeek 1971, des Lauriers 1994, Adam & des Lauriers 1998, Graves 2007). They typically perch or hover near the ground and lick up these substrate particles by flicking the long tongue in and out. Studies of the materials favoured by hummingbirds show that they are high in calcium, soluble salts, potassium and magnesium (Adam & des Lauriers 1998).

Purple-throated carib (Eulampis jugularis), image by Charlesjsharp, from wikipedia.

– A specialised diet of nectar also means that hummingbirds have to produce a lot of urine (note that they also drink a lot of water). A lot. In fact, the urine they produce every day might amount to anywhere between 56 and 149% of body mass (Calder 1979, Calder & Hiebert 1983). For comparison, the urine normally produced by a human in a day amounts to somewhere between 1.5 and 2.5% of body mass. This copious peeing means that hummingbirds are forced to expel a significant amount of the electrolytes their bodies contain: studies of Broad-tailed hummingbirds S. platycercus indicate that they need to replace about 14% of their sodium and potassium requirements every single day (Calder & Hiebert 1983). So this might also link to that ingestion of sediment and ash particles discussed above. There’s also a report of a hummingbird drinking sea water from a sheltered bay (Bacon 1973) – perhaps another effort to compensate for electrolyte loss. If you’re wondering, yes, there are various images and videos online of peeing hummingbirds, but to be honest they don’t show anything particularly remarkable.

Magnificent hummingbird (Eugenes fulgens) caught in act of bill-bending. Photos by Gregor Yanega.

– Mandibular kinesis (the bending or bowing of the bones of the lower jaw) has evolved a few times in birds (most notably in pelicans and nightjars). I don’t think you’d expect it to be present in hummingbirds: after all, they mostly obtain food by poking their long, slender bills into flowers and licking up nectar with a long, protrusible tongue. But, as we’ve just seen, hummingbirds need to supplement their nectar diet with arthropod prey. Their generally elongate, slender jaws aren’t great for grabbing arthropods, so it seems that they’ve evolved a unique form of mandibular kinesis that allows them to catch insects while in flight. No, they don’t try to grab insects with a tweezer-like motion – rather, they open their jaws wide and scoop the prey into the back the mouth (in swift-like or caprimulgiform-like fashion – hmmm…). As they open the jaws wide, the lower jaw tip bends downwards while its two halves bow outwards (Yanega & Rubega 2004). Jaw flexion thus occurs in two dimensions simultaneously: a unique, and very neat, feature. Incidentally, there are no special joints that allow this extension of the gape – it’s all to do with deforming already flexible bones. Remember that we only know about this amazing flexibility because we can use high-speed video to study live hummingbirds: we wouldn’t know it otherwise (Yanega & Rubega 2004).

More later.

For previous Tet Zoo mentions of hummingbirds (and ‘mentions’ are pretty much all that have appeared so far), see…

Refs – -

Adam, M. D., & des Lauriers, J. R. 1998. Observations of hummingbirds ingesting mineralrich compounds. Journal of Field Ornithology 69, 257-261.

Bacon, P. R. 1973. Hummingbird drinking sea water. Auk 90, 917.

Calder, W. A. 1979. On the temperature-dependency of optimal nectar concentration of birds. Journal of Theoretical Biology 78, 185-186.

- . & Hiebert, S. M. 1983. Nectar feeding, diuresis, and electrolyte replacement of hummingbirds. Physiological Zoology 56, 325-334.

des Lauriers, J. R. 1994. Hummingbirds eating ashes. Auk 111, 755-756.

Graves, G. R. 2007. Jamaican hummingbirds ingest calcareous grit. Journal of Caribbean Ornithology 20, 56-57.

Verbeek, N. A. M. 1971. Hummingbirds feeding on sand. Condor 73, 112-113.

Yanega, G., & Rubega, M. (2004). Feeding mechanisms: Hummingbird jaw bends to aid insect capture Nature, 428 (6983), 615-615 DOI: 10.1038/428615a

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.

The views expressed are those of the author and are not necessarily those of Scientific American.





Rights & Permissions

Comments 29 Comments

Add Comment
  1. 1. KarMannJRO 6:28 am 10/3/2011

    One of my recent happy scientific moments was when it occurred to me that, given what I knew of hummingbird metabolism, I would expect them to hit the hummingbird feeders especially hard around dusk and dawn, as they gorge to get through the night (even at reduced metabolism), and fill up their emptied bellies in the morning.
    So I started paying attention to how many hummingbirds I saw when, and, while I wasn’t quite so scientific as to count visits, it was clear that I was seeing some feeding during most of the day, but around sunset & sunrise, there just weren’t enough feeders for them all, and that’s when they really started chasing each other off, guarding their precious nectar.
    Science!

    Link to this
  2. 2. Jurassosaurus 9:50 am 10/3/2011

    Females store extra calcium (for eggs) as medullary bone. I believe standard calcium storage (for body use) is still placed in the bones themselves, especially for the males.

    Link to this
  3. 3. naishd 10:36 am 10/3/2011

    Oops, oh yeah – will alter the text :)

    Darren

    Link to this
  4. 4. John Harshman 11:17 am 10/3/2011

    Another fine peculiarity is of course the habit of torpor, but I suppose everyone knows that. Less well known, perhaps, is that if you mist-net one and lay it on its back in your hand, it will stay there, apparently forever, though it would seem easy for the bird to just get up and fly away. In order to release the bird, you have to turn it over, at which point it will indeed fly away. As far as I know, nobody has ever studied the reason for this behavior. Maybe it’s related to torpor.

    Link to this
  5. 5. Heteromeles 12:03 pm 10/3/2011

    We have two feeders up, and a flock of Anna’s hummingbirds use them. Each of these feeders is small, with only one opening. Interesting social behavior! One feeder is controlled by a large, very dominant male, the other by a succession of adolescent males (fun to watch their bibs growing in. It fills in asymmetrically, one side at a time, and they flash that side preferentially to look older than they are).

    Feeding does indeed pick up about 30 minutes before dusk. Up to three hummers will tag team the big male at the time, each hoping to get a drink while he’s driving off the other two. Funny thing is, the dominant male always leaves before it gets too dark, and then all the others take turns drinking. I’ve also seen the big male allow one really immature bird to drink its fill, when it got so desperate refused to be driven off.

    On the back feeder, I’ve seen up to three immatures hovering around it, taking turns feeding. With two it’s easy, they will alternate going in to feed, back and forth. With three, the dynamics are a bit more complex, but they manage. Typically at least two of these sharers are females.

    I think the idea that hummingbirds are asocial is simplistic. I can identify individual males with little difficulty, and given the way they interact, I’m pretty sure they not only identify each other, but have a dominance hierarchy. They also seem to make accommodations for each other. Take the dominant bird leaving early. I’m not sure whether he’s trying to get first choice of roosting sites or what, but it certainly looks like he’s making some sort of accommodation, allowing the others to feed before they get too desperate, while preserving his dominant status.

    Link to this
  6. 6. naishd 12:18 pm 10/3/2011

    It makes me sad that there are no hummingbirds here in Europe (though there were in the distant geological past: more on this in another article). Believe it or don’t, many people (certainly in the UK) seem not to know this, and they frequently mistake the Hummingbird hawkmoth as an actual hummingbird. Incidentally, there are bizarre Old World reports of hummingbirds that apparently weren’t based on mistaken sightings of hawkmoths – I’ll cover this later; am looking forward to publishing the article on hummingbird-plant co-evolution. Didn’t know that they go into tonic immobility.

    Darren

    Link to this
  7. 7. Hai~Ren 1:06 pm 10/3/2011

    I live in a part of the world where hummingbirds aren’t native, but unfortunately, a number of people mistake the sunbirds for hummingbirds. I wonder if sunbirds possess similar physiological adaptations to cope with a nectar diet.

    The odd thing is, in tropical Singapore, there isn’t really a culture of deliberately feeding birds like in Europe or North America, where people set up bird feeders and lay out seed & suet; here, such attempts would soon get quickly overwhelmed by the large numbers of commensal Eurasian tree sparrows, mynas, house crows and feral pigeons which are so prevalent in urban and suburban areas. The closest we have to bird feeding are elderly folks throwing rice or bread to pigeons, or homeowners planting trees which bear fruit that attract native birds such as bulbuls, fruit pigeons, koel, starlings and orioles, or growing flowering plants to attract sunbirds. Hummingbird feeders, nesting boxes, birdbaths and bird feeding tables are completely alien concepts to the average homeowner.

    Link to this
  8. 8. David Marjanović 1:18 pm 10/3/2011

    Believe it or don’t, many people (certainly in the UK) seem not to know this, and they frequently mistake the Hummingbird hawkmoth as an actual hummingbird.

    o_O

    O_o

    BTW, what did you mean in your Twitter feed by saying physicists are tabloid-prone?

    Link to this
  9. 9. Jerzy New 1:49 pm 10/3/2011

    @4:
    You can do the same (but not always) with European Kingfisher.

    I guess it is weird sensory thing, like reported that tied chicken laid flat with a line drawn extending its bill doesn’t struggle but is like hypnotized.

    Link to this
  10. 10. Jerzy New 1:51 pm 10/3/2011

    @Yet another trivia is that hummingbirds hybridize a lot, and for long it was not sure whether some forms were hybrids or separate species.

    Link to this
  11. 11. ValFisch 4:16 pm 10/3/2011

    Damn this is surreal! Thanks for this Darren!

    Link to this
  12. 12. Heteromeles 4:33 pm 10/3/2011

    Well, hummingbirds eat fruit flies, so having the feeder near the worm bin is an entertaining (albeit partial) fly control method.

    Another interesting episode was when a bird panicked after flying inside. It buzzed around the room, beak pressed to the white roof. Although the door was open, it couldn’t bring itself to drop down enough to fly out. I got it out by raising the hummingbird feeder (which is on a post) until it was at the bird’s eye level. It took about 30 seconds for it to come over to refuel. While it was feeding, I gently lowered the feeder through the door with the bird in tow. As soon as it was outside, it flew away.

    Link to this
  13. 13. Ranjit Suresh 7:16 pm 10/3/2011

    @Heteromeles: Do hummingbirds frequently collide with windows like other birds? I would imagine their small size could make them especially vulnerable to this.

    Link to this
  14. 14. Heteromeles 8:22 pm 10/3/2011

    @Ranjit: It happens (e.g. http://birdsmack.wordpress.com/category/ruby-throated-hummingbird/) However, I’ve never seen it.

    Link to this
  15. 15. vdinets 8:29 pm 10/3/2011

    Ranjit: yes, they do. (But why do you think it has something to do with size? I don’t follow.) I saw it only once, in Mindo (a town in Ecuador where birding visitors are a major source of income, so almost every house has hummingbird feeders and they are very busy). Owners of the place where it happened told me that they have hummingbirds collide with windows once every few days. Their children have been taught to pick up such birds immediately to save them from cats. Usually the birds recover after a few minutes. Interestingly, these people claimed that they’ve never seen a bird damage its bill in such a collision.

    Link to this
  16. 16. naishd 4:24 am 10/4/2011

    On the issue of controversial hybrids/possible overlooked species mentioned by Jerzy (comment 10), there’s at least one hummingbird species that was conventionally identified as a hybrid but now seems distinct: the Bogotá sunangel Heliangelus zusii, known from a unique Colombian specimen collected in 1909 (Graves 1993).

    And there are also hummingbirds that were long misidentified as members of other species but are now thought to represent poorly known, now extinct, taxa, like Brace’s emerald Chlorostilbon bracei from New Providence in the Bahamas. The only known specimen was collected in 1877 (Graves & Olson 1987).

    Things sometimes go the other way round – that is, supposedly distinct species turn out to be hybrids. The Quito purpleback Lesbia ortoni (based on a single specimen from Ecuador) was shown by Graves (1997) to be a hybrid between a Black-bellied trainbearer L. victoriae and a Purple-backed thornbill Ramphomicron microrhynchum. Gould’s woodstar Acestura decorata also turned out to be a hybrid between two other woodstar species, and there are others too. However, while hybridisation in hummingbirds (sometimes intergeneric hybridisation: Graves & Zusi 1990) does seem to be a fairly regular occurrence, some supposed hybrids were seemingly over-enthusiastically interpreted and are merely “normal individual or age variants” of the species involved (Binford 1985).

    Refs – -

    Binford, L. C. 1985. Re-evaluation of the “hybrid” hummingbird Cynanthus sordidus × C. latirostris from Mexico. The Condor 87, 148-150.

    Graves, G. R. 1993. Relic of a lost world: a new species of sunangel (Trochilidae: Heliangelus) from “Bogotá”. The Auk 110, 1-8.

    - . 1997. Diagnoses of hybrid hummingbirds (Aves: Trochilidae). 3. Parentage of Lesbia ortoni Lawrence. Proceedings of the Biological Society of Washington 110, 314-319.

    - . & Olson, S. L. 1987. Chlorostilbon bracei Lawrence, an extinct species of hummingbird from New Providence Island, Bahamas. The Auk 104, 296-302.

    - . & Zusi, R. L. 1990. An intergeneric hybrid hummingbird (Heliodoxa leadbeateri × Heliangelus amethysticollis) from northern Colombia. The Condor 92, 754-760.

    Darren

    Link to this
  17. 17. naishd 4:30 am 10/4/2011

    On the subject of hummingbirds falling on the ground, colliding with things, etc., has anyone seen what happens when fighting hummingbirds fall to the ground mid-battle? Must look for videos online…

    Darren

    Link to this
  18. 18. KarMannJRO 7:35 am 10/4/2011

    …known from a unique Colombian species collected in 1909….

    Layperson’s question here: Is this a special jargon use of ‘species’? Or a typo for ‘specimen’, which is the word I’d usually expect there?

    Link to this
  19. 19. naishd 7:44 am 10/4/2011

    It’s a typo, my bad. Am gonna correct it now, thanks.

    Darren

    Link to this
  20. 20. Heteromeles 2:59 pm 10/4/2011

    I’ve never seen fighting birds hit the ground. In fact, I rarely see (or hear) them hit each other. A video would be great.

    Link to this
  21. 21. Carkeef 6:36 pm 10/4/2011

    My friend and I live in Virginia and were wondering how hummingbirds migrate south for the winter. We were thinking we have never seen a group flying south in v formation like other birds……and how far south do they travel?

    Link to this
  22. 22. John Harshman 12:16 am 10/5/2011

    Carkeef: Pretty far south. Your Virginia hummingbirds fly straight across the Gulf of Mexico to Central America.

    Link to this
  23. 23. Jerzy New 7:45 am 10/5/2011

    @21
    And most small birds (unsure about hummingbirds) usually migrate high and at night to avoid hawks, so you don’t see them on migration.

    Link to this
  24. 24. deang 10:31 pm 10/5/2011

    Hummingbirds do fly into windows like other birds, maybe even frequently. A friend in central Texas lives in one of those mid-century-modern-style houses with huge expanses of window and theirs is set right in a woodland overlooking a creek. Small birds of all kinds are frequently killed crashing into their windows, and they save their bodies in a freezer. They have many specimens of the two local hummingbird species, Ruby-throated (Archilochus colubris) and Black-chinned (A. alexandri).

    When my sister lived in Houston, hummingbirds sometimes got their bills stuck in the screen of her porch and would pass out. When my sister would find them, she’d hold them in her hand until they revived, offer them some sugar water from a feeder, and then they’d perch on her finger for a bit before flying off. I assume they were pursuing insects on the screen or something.

    Link to this
  25. 25. victorg 2:33 pm 10/7/2011

    In some poor, rural communities in Brazil, it’s reported as usual for birds to hit (reportedly, only white) walls and fall stunned on the ground. Most of the tales I heard also cite the revivification method: cover the bird with a cooking pan and bang on it as hard as you can with a wooden spoon. Take it off and away flies the bird (in a rather poor condition, I’d guess).

    Link to this
  26. 26. UK_wildlife 6:47 pm 10/10/2011

    Is the whimbrel in the bottom whimbrel photo doing this Mandibular kinesis? I presume its an adaptation to getting prey form the mud. http://www.uk-wildlife.co.uk/yellow-legged-gulls-whimbrel-and-ring-necked-parakeet/

    PS the link is to my new site

    Neil P

    Link to this
  27. 27. naishd 7:38 pm 10/10/2011

    Neil: yes, you’ve nicely captured a Whimbrel in the act of distal rhynchokinesis. Most long-billed waders can move the jaw tips like this – obviously pretty useful for grabbing small prey in confined spaces or in sediment (some waders also use it to grab moving prey in water).

    Darren

    Link to this
  28. 28. Mu... 12:59 pm 10/12/2011

    Hmm, guess I should mix my hummingbird solution with mineral water instead of filtered. Buggers went through 30 pounds of sugar this summer, I had 18 hovering around one feeder at a time in one picture.
    Oddly enough they fight over the red feeder with the yellow flowers and ignore the yellow one with the red flowers 15 ft way half the time. Same solutions, just the color scheme is different.

    Link to this
  29. 29. Zeezee 11:52 pm 01/27/2014

    How can these little guys survive temperatures well below freezing??? This winter we have had at least 3 different hummingbirds that never migrated. Our temperatures were sub freezing for over a week a
    few times. It was -10°C at night & -6°C in the day. I had to keep 2 feeders on the go so I could swap them out once the other had frozen. I was concerned I was stopping them from migrating by keeping the feeders out there but I read online to keep them out for 2 weeks after the last hummer is seen. Where do they get protein at those temperatures?

    Link to this

Add a Comment
You must sign in or register as a ScientificAmerican.com member to submit a comment.

More from Scientific American

Scientific American Special Universe

Get the latest Special Collector's edition

Secrets of the Universe: Past, Present, Future

Order Now >

X

Email this Article

X