Notes: This abandoned bird’s nest appeared on a lawn beneath an apple tree. Materials comprising the nest appear to include straw/grass, pine needles, synthetic fibers, and an outer layer of lichen. We think the bird which built this may be a Blue-gray Gnat Catcher.
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later this week.
If it’s not much trouble… Jason Hollinger, 1123 Hunter Lake, Reno, NV 89509
then I will mail it to you.
Karen took another close look ans she thinks there may be three lichen species. But we have pretty-much reached the limit of our lichen knowledge as it applies to this obs.
Thanks Jason. Maybe another nest will become available for observation. We often find bird’s nests here and there on our property.
I think we can confirm Parmelia sulcata (not Parmelia squarrosa) now, because I see a few marginal linear soralia. (P. squarrosa would have isidia instead and over the surface, not concentrated in soralia, marginal or otherwise.) So this is definitely a very discerning gnat catcher!
But oddly, there is another species here, too. The close-up shows mostly Parmelia — thick, gray, squared-off lobe tips, lots of irregular white mottling — but also some thin, rounded, faintly yellowish, unmarked, rounded-off lobes. Your extreme close-up of two pieces shows this species. It also has cilia, ruling out just about everything but Parmotrema and Myelochroa aurulenta. Since it’s the same size as the Parmelia (plus or minus), I think it’s the latter. (I’m not seeing any soredia on it, which should occur on pustule-like swellings. That would clinch the id.)
So if the bird is not using local material (mostly Flavoparmelia caperata and Punctelia rudecta according to associated observations), it’s going out of its way to find particular species. But there are scarcely any similarities between Parmelia sulcata and Myelochroa aurulenta! I was thinking rhizines at first, because Parmelia sulcata has those bottle-brush velcro-like rhizines, presumably useful for getting bits of lichen to stick to a nest. But Myelochroa aurulenta doesn’t, it just has scattered simple stubby things.
Chemistry is unusual in M. aurulenta — leucotylic acid, a fatty acid, in addition to atranorin. P. sulcata has atranorin and salazinic (possibly not found in other common species in the area). F. caperata has usnic acid and caperatic acid (another fatty acid). Punctelia has mostly atranorin and lecanoric acid. I’m not sure what salazinic and lecanoric acids are good for, unfortunately. In any case, the chemistry of the Myelochroa and Parmelia are not at all related. Many local foliose species have atranorin (sun-screening bluish-grayish pigment), but it’s singling out two species. Usnic acid has all sorts of good uses, including sun screening and herbivore defence, so it doesn’t per se make much sense that it would exclude it. (There’s probably a reason Flavoparmelia caperata is so successful in the area!)
Camouflage is certainly a good hypothesis, but to me it begs the question of why it would be so particular about species. Unless it were a mechanical thing — e.g., Parmelia is easier to remove intact (~looser and thicker lobes) and sticks better to the nest — but then why add Myelochroa which is none of these things?
Sure has me stumped!
Fascinating observation, thanks for taking the time to do the follow-up.
I wonder how much more we can do without seeing additional nests from the same area and other areas. I wonder how good our conclusion is that this gnat catcher is being particular about species, just because only two happen to show up in this nest. Maybe he has a favorite roost or perch which happens to have these two species in abundance?
Time-savers are appreciated!
You can link to other observations easily if you just type _observation 166988 _ or _obs 166988 _, just remove the extra space like obs 166988 and adjust the observation number accordingly. You can find other cool options by clicking the Textile markup system found just below the comment input box. :)
hopefully show some additional details. I’ll get back to this…
Checking the trees near where the nest was found and there’s lots of this lichen.
But the nest appears to show none of this (possibly Flavoparmelia caperata).
Also observed plenty of this on the trees.
Looked like the type used in the nest, but there was (at least) one notable difference. Taking a look at the last posted photo in the nest obs (166988 pic of two lobes) one sees multiple black rhizines. Examining a few pieces of the lichen in the second link above (167373), I found only two rhizines. For the moment, I’m assuming that relative abundance of rhizines may indicate different species. But perhaps the rhizines deteriorate as the lichen matures/persists?
At any rate, the Flavoparmelia showed no rhizines at all. So this evidence points toward supporting Jason’s hypothesis about the rhizines providing the advantage of anchoring the lichen to the nest. I wonder if the birds target this one species, or do they randomly check lichens until they find one with sufficient numbers of rhizines?
Motivation seems to another question. Why do these birds add the lichen to the nest? Seems like a lot of work, and the lichen seems to offer little in the way of supporting structural integrity. I like the camouflage idea.
an ornithologist at Wilkes University. Here is what he said, “Yea, that is interesting. I have noticed that all the hummingbird and gnatcatchers nests seem to have the same lichen species – or related species. Whether they smell for them, though, is a bit questionable. I don’t see why they couldn’t but their eyes are superb. I wonder if there are large patches of these lichens on trees or rocks and that attracts the birds then they use sight to get particular pieces.”
Karen had the idea that the lichen may help to camouflage the nest. We still haven’t examined the isidia/soredia… getting around to it.
to see how good a lichenologist this particular blue-gray gnat catcher was! I’ve heard sometimes they can be very discerning. I wonder if maybe the salazinic acid in these two species of Parmelia is good for keeping out lice or something, and maybe they can smell it(?) Maybe this is a falsifiable hypothesis: I just need to look up what other common species in your area have salazinic acid and are of similar size and construction qualities! Both these species of Parmelia have squarrose rhizines, though, a fairly uncommon characteristic that might make them cling to the nest a bit like velcro. We may just have to ask them…
Karen knows more about lichen than I. Maybe she can examine the isidia/soredia, and I’ll see about additional photos.
Looks like the lichen name is more elusive.
Adam Searcy, curatorial assistant at the Western Foundation of Vertebrate Zoology (home of one of the largest egg and nest collections in the world), who said it was ‘spot on’ for Blue-gray Gnatcatcher.
Ruby-throated Hummingbird nests are smaller than this one. Dimensions for this nest are: 2.5 inch diameter (width), 2.5 inch height, interior 1.9 inches deep, opening 1.2 inch diameter.
We have a feeder on the front porch, so there’s plenty of hummingbirds zipping around. Karen thought the nest was actually a bit large/deep for a hummingbird. One of our bird books mentions that the gnat-catcher often uses lichen as a construction material. I mailed the photos to my brother who’se active in the Audubon. Maybe he will offer a suggestion.
but otherwise looks good for a gnatcatcher.
Did you consider Ruby-throated Hummingbird? Size would probably tell them apart.
Created: 2014-06-08 21:55:58 CDT (-0400)
Last modified: 2014-06-16 07:56:58 CDT (-0400)
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