Reader Bruce Lyon sends some photos of nesting Norther Harriers and a really nice story of their breeding biology and appearance:
In April I found a Northern Harrier (Circus cyaneus) nest along the coast north of Santa Cruz in California. Harriers nest on the ground in marshy or brushy areas. Female harriers do all of the incubation but the male brings her food (mostly mice) while she incubates. The food is delivered in an aerial transfer: the female chases the male until he drops the prey item, which the female then snatches before it hits the ground. I knew the harriers had to have a nest in a patch of scrub because I saw several aerial transfers in the spot. In each of these, the male arrived with a mouse, gave his distinctive “I have a mouse” call, which brought the female up off the ground to get the mouse from the male, and she then returned to the same spot of ground. I knew the nest had to be within a ten by ten meter square area but I could not find it, both because the vegetation was dense and the female sat very tightly on the nest refusing to budge. Eventually I came within three feet the nest and the female flushed, and I was treated to the most adorable baby raptors I have ever seen. In the photo below below two chicks have just hatched and eventually all five eggs hatched:
The nest (bottom center of the photo) is in coastal scrub right next to the coast:
The female continued to bring in nesting material even after the chicks hatched. Here she is about to drop down to the nest:
Both parents dive-bombed me quite a bit the few times I checked the nest but they never actually hit me with their feet or talons. Some birds of prey will strike, and some can do serious damage. The pioneering English bird photographer Eric Hosking lost an eye to a Tawny Owl (and later wrote a book with the amusing title “An Eye for a Bird”). This is the female turning to come at me:
Female threatening with her feet:
Below: The male on his favorite perch. This species is quite dimorphic in plumage coloration—females are a lovely warm brown color while males have a pearly gray plumage coloration. I see mostly female plumage birds along the coast north of Santa Cruz and have often wondered if the sex ratio is really biased. In a related species in Europe (Marsh Harrier) it was recently discovered that some males bear female plumage their entire lives so I now wonder if something similar could be going in Northern Harriers. (Sternalski et al. 2011. Adaptive significance of permanent female mimicry in a bird of prey. Biology Letters 8:167-170). Spoiler alert: males with female plumage are treated with reduced aggression by territorial males in full male plumage.
Male leaving the perch to come and voice his concern to me:
Male in flight:
Male coming in for a landing:
Below: Harriers have facials ruffs (or disks) that make them seem like half hawk, half owl—the resemblance seems to be an example of convergent evolution. Like many owls, harriers can accurately locate prey entirely by sound cues and their sound-reflecting facial ruffs are similar to those found in owls. Bill Rice, now well known for his experimental evolution studies with Drosophila, did his PhD work on harriers and showed that (1) in the lab harriers are as accurate as many owls in locating sounds, and they are far more accurate than other hawks, and (2) wild harriers in the field can accurately target mouse-like sounds emitted from hidden speakers (“mouse-like” because Rice made the sounds himself after practicing to sound like a Microtus vole). Rice WR 1982 Acoustical location of prey by the marsh hawk: adaptation to concealed prey. Auk 99:403-413.The facial disk of the female (left) of my pair was much more distinct than the male (right) but this may be due entirely to contrasting color of the egg of the ruff on the female. According to species accounts for harriers, the brown eyes of this female means she is a young bird (one year old); older females have yellow eyes:
Reblogged this on Johnnypolitico's Weblog and commented:
Georgeous
Stunning photography.
Great post!
+1! 🙂
Those are excellent photographs, but I have to say that disturbing a nest is frowned upon by serious birders. If you posted this on birding photo-sharing sites you’d come under extreme criticism. Many sites ban such photos outright. (I’m not allowed to post my nesting eagle on Facebook Birders, for example, even though I take them from far away.) Personally, I have no objection to a one-time intrusion, as long as it’s kept to a minimum and the location of the nest isn’t divulged, but many birders would tear you a new one.
http://www.aba.org/about/ethics.html
Hmmm, I’m all for exercising restraint and caution, but codes of ethics often sound a bit like the First Rule of Fight Club.
Frankly I’m more impressed by that Tawny Owls will tear me a_real_ one. Nesty birds.
Thanks Stephen. I am aware of this issue and for that reason I only checked the nest a couple of times. Perhaps to put it this issue in broader context, in my research as a scientist (avian ecology and behavior) I study breeding bird behavior and some of my studies of waterbirds and songbirds involve checking nests daily! No other way to get the data. Based on years of checking thousands of nests I have a very good sense of the difference between short term and long term influences. The birds get a bit upset but compared to their daily trials and tribulations, in my opinion a brief visit by a scientist or photographer is not the end of the world.
What I think deserves more attention is the clueless or unscrupulous photographers that cause birds to desert. This is a particularly issue with birds of prey as they are often very prone to nest desertion. I have come across situations where photographers caused hawks to desert their nests.
Another similar bird ethic question that is much discussed among birds (including serious ones!) is the ethics of using song playbacks to attract birds. Like nest checks this does have a short term effect on the behavior of the birds (males get pissed off and look for the rival that is singing on their territory) and an open question is how big an impact this has.
Good for you, Bruce. The photos, especially the one of the nest, are sublime. I can imagine how your heart must have skipped a beat when you found it. I know I’d have been too excited and worried about upsetting the parents, never mind other birders. But there’s no other way to study them, from cradle to grave, as it were. I once got very close to a big Canada Goose nest with a sizable clutch of eggs. I wanted to see how many there were, and devise a way to protect them from the construction crews. Anyway, the parents really came after me that time, honking and wings spread widely, and fighting mad.
Oh, and I should have mentioned that the harriers decided to nest 50 feet from a walking trait that gets moderate use. They are pretty used to people being close to their nest. More and more raptors are moving into urban environments and a bit of human disturbance becomes inevitable. Coopers Hawks nesting in city parks and along city streets is a prime example.
Harriers nest on my ranch. I’ve been tempted to locate and photograph a nest, but so far I’ve resisted. Your photos are spectacular. I didn’t realize you were studying these birds scientifically.
We’ve had a problem with people disturbing owls in populated areas. The word gets out on the Internet that some rare owl or some nesting owls are in a particular location and crowds of birders and photographers flock to it. It got so bad that my local Facebook birding group banned owl photos altogether.
Which situations sometimes lead to birders withholding information from other birders, leading to a lot of animosity in the hobby…
Recently, a Facebook friend of mine (and an excellent photographer) unintentionally got too close to a Red-shouldered Hawk nest. (He didn’t know it was there.) The bird attacked him and he sustained a head wound serious enough to send him to the emergency room.
Thanks for this lovely post. I love watching harriers here in Montana, and grateful to know more about them now due to this great site!
Those little chicks are too cute. Terrific photos and commentary, thanks for brightening my morning with Harrier learnings. 🙂
Wonderful images.
…the egg of the ruff on the female?
A typo, I think.
Another attack story – a friend of mine was studying nesting in Great Horned Owls, which required climbing trees to check nests. No trouble at most nests – the parents flew away when he climbed up to their nests – but one brooding adult took off, apparently flew away, but actually flew in a wide loop, came back towards the tree at daisy-clipping height, flew up the trunk behind my friend and set its talons in his gluteus maximus.
A lot of hilarity about this later – we were all grad students at the time – but he sustained serious gouges and had to go to Emergency, after he’d been gotten out ot the tree.
I’m sure that was an autocorrecto for what was meant to be “edge.” 🙂
Aargh, I wouldn’t want a Great Horn’s talons anywhere near me! Science can be dangerous. 😀
Thanks for a wonderful story & illustrations, Bruce! While quite familiar with the harriers’ facial discs, it had never occurred to me that they served the same function as the owls’. (Now I feel stupid.) I love the watch harriers cruising low over the fields.
Wonderful BIF’s! It always a thrill to see a true Gray Ghost. It was my impression that the same young-male plumage story had been confirmed here in the States, as well. Which makes me wonder now about all those harriers I eBirded as females…
That last comparison of faces is fantastic!
Wow, wonderful photos! Thanks!