One of the most alluring behaviors about birds is that of building a nest. This is obviously a fundamentally important task for most bird species, and it is equally important for us to understand the nesting process of each species if we are to make sound conservation decisions. Most of us love an “Easter Egg hunt”, and as a bird biologist, I love sleuthing around the woods and fields for bird nests – I’m sure it’s the thrill of the hunt, and I’m lucky to be able to play out my childhood afflictions in my adult, professional life. I have been recording nest data on North Carolina birds for over 20 years. I’m continually surprised at how little we know, still, about a number of the species that breed in our State.
On the one hand, there are programs to monitor certain groups of birds, such as those we call “colonial nesting waterbirds”, like the coastal-breeding terns, or egret, species. On the other, there are still a number of species for which we have almost no nest data; or, those which we have are 100+ years old. I study the breeding biology of a few species, but when engaged in my projects, or on public field trips, I keep an eye out for any nest behaviors. This past spring, I and the Museum’s bird collections manager Brian O’Shea, came across a dozen or more nests, two of which were “firsts” for me, others nearly new for me, and others just plain neat to view. Included here are some observation notes about some of these nests, and some photos, when we could get those.
First things first.
Worm-eating Warbler (WEWA) – this Neotropical migrant species is now a “species of concern” in the Southeast, as it appears to be declining in numbers. I have found birds carrying food before, which most birds do when feeding nestlings somewhere; but I was unable to follow those birds to the nests. In mid- May of this year, while studying some breeding Black-throated Green warblers in the Uwharrie mountains region, I again came upon an adult carrying food. This time, I was able to hide far enough away, yet still watch the adults, and figure out where they were going with the food. It took over an hour, because they were weary, and on the slope of a ravine that was partially obscured from me. This species nests on the ground, and often at the base of some vegetation. There was little vegetation in the area to where the pair kept going, and I was able to locate my first Worm-eating Warbler nest underneath an overhanging “soffit” of dirt/moss, near the base of one of the few Mountain laurels on the hillside. The nest contained 3 babies, which were beginning to “feather out”. I quickly took some pictures and kept moving.
Later, when reviewing the images, I realized that the front nestling was a Brown-headed Cowbird. This species lays its eggs in other birds’ nests, leaving the host to raise any cowbird that hatches out. Often, the cowbird eggs hatch first, and those babies grow quicker than any host young, and as such, the host young often perish (or are literally tossed out of the nest by the baby cowbird). In this case, I guess because the nest was on the ground, although the cowbird certainly looks larger, the two warbler nestlings look healthy enough, and my guess is that all of them eventually fledged. I was unable to go back and check. It was a surprise to see a cowbird chick because the nest site was within a very large patch of fairly mature forest. But we have learned over the past few decades that cowbirds do penetrate miles into such deep woods, and they are masters at finding other species nests, especially ground nesters.
Blackburnian Warbler (BLBW) – on June 5, 2012, Brian and I, along with Marilyn Westphal and Mark Simpson, were scouting along the Big Butt Trail just west of Mt. Mitchell, assessing the feasibility of studying Veery and Hermit Thrush along this trail. Along the way, I spotted a female Blackburnian with food, and instinctively hollered “she’s got an active nest somewhere nearby, follow that bird!” Well, perhaps a bit overly dramatic, but this was to be my first nest for this species, anywhere, and certainly one of the few documented for NC. Within a minute, this female flew to the end of a Red Spruce branch about 30’ up, and Brian announced “I have it.” And indeed, just like that, there it was, a small blob of plant fibers tucked into the leafy, terminal sprigs of a spruce tree. It was too high to determine the number of young or their age, but still an exciting find for us. And just as exciting (or perhaps more to some) were the many male Blackburnians we saw along a one-mile section of this trail. Attached images are a female foraging in red spruce/fraser fir. This migratory species heads to South America after the breeding season.
Winter Wren (WIWR) – soon after finding the above warbler, we began our way back to the parked car. As we approached a large, upturned root ball, a small brown object gently fluttered past me. I had found only one Winter Wren nest before, about 20 years earlier, but in the same “root ball” situation (and they are well-known for nesting in such sites). I was sure it had a nest somewhere underneath but upon kneeling found it to be rather dark and more spacious than I’d thought, as the root ball had an overhanging “porch roof” of nearly two feet. But Brian had his headlamp along, and with his help, I quickly spotted the classic globe of moss that makes up a typical winter wren nest – and noted the other typical feature, that of feathers lining the inside. Brian determined that there were 6 eggs inside. It’s a large nest given the birds’ size, with a side entrance; and I imagine that the thick layer of moss, plus those feathers, provide for nice insulation on those cold mountain nights, which extend into late June (in NC, Winter wrens breed from 3000-the top of Mt. Mitchell). The forecast for the coming night was for lows in the upper 40’s, and remember, this was June 5th.
House Wren (HOWR) – when I returned home to Raleigh on June 8, the wren eggs in the nest box alongside our driveway had just hatched. This nest contained 6 eggs as well. House and Winter wrens weigh in at about 10g or less, and I still have a hard time understanding how they can even attempt to raise 6 young, let alone lay 6 eggs. Both of these species are in the same genus, Troglodytes, which translates to “cave dweller” and are what we call “short distance” migrants – they essentially do not go south of the border.
Black-and-white Warbler (BAWW) – I had another bit of positional luck in the Uwharries this spring. On May 8 we were trying to capture another Black-throated Green Warbler for our study of that species, and when we sat down some 10 m from the mist net, we saw some activity to our right. There was an adult female Black-and-white, with a big wad of food in her beak. By now, you know my reaction to such sightings! She was quite close to us, less than 10 m, clinging to the side of a small tree that was part of a group of 3 smallish trees. This species is also a ground-nester, so I was sure she had a nest at the base of one of those trees, and indeed, she did. BAWW’s do not seem to be as shy around the nest as some other species. Within a few minutes we had captured the Black-throated Green we were after, and I moved our banding operation a bit further away, but only about 12 m from the nest site. She, and soon after her mate, immediately began going to the nest, feeding the 5 nestlings. The nestlings seemed to be about 5 days old, and in this species, fledge at about 9 days old. Indeed, I returned on May 14 and saw one fledgling following the adult female, and being fed by her, about 15 m from the nest site. This is only the 3rd nest of this species that I have found, although I have often seen adults carrying food for nestlings.
Wood Thrush (WOTH) – there is much concern about the fate of this Neotropical migratory species these days, as population numbers have plummeted over the past few decades. In urban areas, this species still occurs but is usually a host for Brown-headed cowbirds. Thus, in any area, we are interested in how it fares during the breeding season. As indicated already, cowbirds are found even within large areas of mature forest. On May 7, again while tracking a Black-throated Green Warbler on Daniel Mountain in the Uwharries region, I happened to look to my right and spy that suspicious form in a small mountain laurel alongside the trail. A closer peek revealed a female sitting tight in her nest. I was able to climb the bank and get on level with the nest, and even slightly above, and take some images of her –a veritable “birds-eye view”. When I retreated and went back down to the trail, she bolted. My guess is that she knew she had been found, but was not going to risk any movement, and thus detection, while I was looking at her. Thus, as soon as I took my eyes off of her to go back to the trail, she felt safe to make her escape. At that point I decided to go back and see the contents, again to determine if there were any cowbird eggs or not. As you can see from the image, they were all Wood Thrush eggs. You may be surprised by how similar they are to a Robin’s egg – well, a Robin is in the thrush family and thus these two species are closely related. (Bluebirds are also thrushes). I was back in the Wood Thrush area on May 16th, and with the help of a mirror determined that the eggs had hatched and the young appeared about 3 days old. I did not want to disturb the nest area any more so did not climb the bank again to take any more photos.
Dark-eyed Junco (DEJU) – this species requires no luck at all to find its nest, nor hardly any effort. Indeed, it’s when you don’t find one after spending a few minutes in the mountains above 3500’ that you should begin to worry. So, what’s the big deal then? A couple things. For one, when we can acquire a lot of data about an animal, we can better track changes over time. Thus, it’s prudent to also keep recording nest data for at least some of our more common species, across their range (whether that be elevational, like a junco, or longitudinal, like towhees). Another is to document a range of behaviors. The Dark-eyed Junco is typically a ground nester, usually doing so underneath a dirt overhand along a road or trail, where some herbaceous cover hangs over as well.
In early June, Brian and I were capturing Hermit thrushes along the Pearly Crockett road, just south of Mt. Mitchell. As I backed away from our mist net, I brushed a very small red spruce sapling, and out flew a junco. Naturally, I peeled back a branch, and there was a nice, rather large-for-a-junco nest, with 3 eggs. Some images are included. Juncos are known to build nests off the ground, but it’s uncommon. I have seen a lot of Junco nests on the ground, but they were never as large as this one, and I suppose being off the ground means you need a little more insulation. I carry a measuring tape with me, and this nest was 1 m above the ground; the inside diameter was 6 cm, the depth of the cup was 3 cm, and the overall width of the nest was 12 cm. But the side that faced the outer part of the tree was broader; that is, the nest width on that side was twice the width of the part that faced the sapling trunk; I think of these as landing pads for an approaching bird (we often saw this in the many Swainson’s warbler nests we measured). Later on down the road we found a rowdy flock of teenaged juncos, at least 10 juveniles about a month out of their various nests. I swear juncos nest all year round! They are one of the most prolific breeders I know.
Yellow-bellied Sapsucker (YBSA) – while on our annual mountain birding trip, May 18-20, we came across quite a few nests of various species. In NC, sapsuckers are a rare breeder in the mountains at various scattered locations, between 3000-5000’ elevation. I studied nesting sapsuckers for a few years, with several colleagues, at 3 sites, including Moses Cone Park. Our now-annual trip includes a morning at Trout Lake in the Cone Park and I cannot resist looking for my beloved sapsuckers and any nests. Indeed, they seem to come looking for me, although it’s been 6 years. During our study, we found that they preferred nesting in dead snags within live red or sugar maples, or black locusts. But this year, along Trout Lake, I found two active nests and both were in dead black birch trees. Mid-May is when the adults are incubating.
During our study we were able to use a camera mounted on a pole that extended up to 55’ and thus we were able to document clutch size. In the first year, we got data on over 25 clutches and all were of 6 eggs. In the second year, there were two snow storms in late April which is right before they begin laying, and in that year, all the clutches were of 5 eggs. Cause and effect? We don’t know, but I’m suspicious. And how does one know when a cavity some 30 or 50’ up is “active”, without the camera? In both cases, we witnessed an incubation “exchange” – in sapsuckers, and apparently most woodpeckers, males take the night shift, so during our morning sojourn we apparently had just the right timing, as the females came in to check on things, and the males departed. That’s certainly one good way to keep your man from staying out too late at night and boozing it up (on fermented birch sap “beer” no less…..).
Empidonax flycatchers – for years Curtis Smalling has observed two species of this genus – Least and Willow flycatchers – nesting at the Valle Crucis Community Park. This is one of our stops on our spring mountain birding trip. This year, we found females of both species building a nest. Most interesting was the Willow, which was just beginning the process. There were only a few strands of plant fibers draped over a small branch, in the early afternoon of the 18th. She must have begun right after “lunch”. Four species of Empidonax flycatchers nest in NC: Least, Alder, Willow, and Acadian. But there are few reports of any Empidonax flycatcher nests for NC. At Valle Crucis, we also found another small flycatcher, the Eastern Wood-pewee sitting on a nest, apparently incubating.
Ruby-throated Hummingbird (RTHU) – although many nests of this species have been found throughout the southeast, one never gets tired of seeing another. Indeed, I think I’ve only seen ~10 in my life. On our mountain trip, Brian outdid himself by finding not one, but TWO nests; one at Trout Lake, and the other at Valle Crucis. The VC nest is shown here, and was “in construction”. The TL nest was done and the female was incubating/brooding, nicely shown in the image. In hummingbirds, once courtship and mating has taken place, the female does the rest, building the nest, and raising the young. And she holds her own territory to do so, driving away conspecifics, including males.
Cedar Waxwing (CEDW) – in NC, this species nests primarily in our mountains, with occasional reports in other parts of the State. On May 18 we found a pair building a nest alongside the parking lot of the Cone Manor House, at the Moses Cone park. We watched the female make several trips, bringing soft plant fibers with which to line the nest. Each time, the male would follow and watch over the activity. The nest site was only about 35’ above us, and we had a great view.
Other nests we found on our mountain trip: Yellow Warbler (YEWA), Red-breasted Nuthatch (RBNU), Baltimore Oriole (BAOR).
Great Crested Flycatcher (GCFL) – this flycatcher is another Neotropical migrant, and a cavity-nesting species. They use “previously owned” cavities. It is a species that returns to our area in late April, but for some reason, I have found numerous times where they returned to our neighborhood at this time in west Raleigh, but began nesting in late May or early June. Most birds begin nesting soon after returning from their “winter” quarters. Such was the case this past Sunday, June 9th, in our front yard. I was out doing some gardening, when down came a female, spiraling right to the ground. I seldom see them go to the ground for food – rather, it’s almost always for nest material. Of course, I wanted to holler out, “she must be collecting nest material!” but sadly, no one was around to hear me.
Nonetheless, she did begin picking up pine needles and some oak leaves, and then flew up to a snag in our neighbor’s tall Loblolly Pine. I was a bit disappointed, because last Fall I had hung a bird box with a hole specifically for Great Crested Flycatcher; and she flew right past that box and on up! This species has nested in other boxes of ours, twice, over the past few years. But not this time. Perhaps the “candy peanut orange” paint job dissuaded her. On the other hand, it’s hard to compete with the site she chose: an old Red-bellied Woodpecker nest, with an east-facing entrance, and 17m (55 feet) up (HINT for the man who has everything: I LOVE my new laser range finder!). This species requires a hole slightly larger than that used by/for bluebirds, should you wish to try for a GCFL pair of your own.
Red-shouldered Hawk – we have had an active nest just a few houses away, all spring. On June 11th, the nest appeared empty, and it would make sense – the nest has contained only one nestling and it’s been growing fast (young of this species often fledge later in June). Young of this and related hawks, like the familiar Red-tailed, usually venture out among nearby branches as they mature, but I was unable to find this one youngster on the 12th, anywhere in the tree. Then on the 13th it was back in the nest. I watched it for about 15 minutes, while taking some photos, and it did indeed take one walk out along one branch, spent a few minutes looking around, and then walked back onto the edge of the nest. This species usually lays more than one egg, 3-4, and the female likely did. From the looks I got of her, and her eyes, she seemed to be a younger adult. The eyes still had a fair amount of yellow, whereas the older birds, those 3+ years, have dark eyes. The nest is way up in a very tall Sweetgum tree, and yes, I was elated to have my laser range finder in hand for this one! The nest clocks in at ~85 feet (26-27m). Now, that’s a room with a view.
And what about that study of breeding Black-throated Green warblers? Well, we had some radio transmitters on a few males, and although my field technician found one of the males feeding fledglings (already out of the nest), we never did find a nest. The same thing happened last year. I’ve only found one nest ever, and that was near Mt. Pisgah. It was about 60’ up in a Chestnut Oak tree, near the tip of a long branch, typical for this species and others like it (e.g. Blackburnian). The thrill is on……..
– John Gerwin, Curator of Birds, Museum of Natural Sciences
DEJU, BLWA, YBSA, WEWA, WOTH, BAWW, RSHA, GCFL – John Gerwin
RTHU, YEWA – Dan Harvey
BAOR, RBNU – Sue Harvey
WIWR – Brian O’Shea