Avian generations in the making – part 2B: nesting in nature

My last blog looked at birds’ nests in man-made structures and there are plenty of birds who take the opportunity to use such sites. Most birds, however, make their homes out in nature – in shrubs, trees and on the ground. This is a bit of a long blog but I want to share views of different species at work.

There are different types of nests; a few types that we see in North Carolina include:

  • Cavity nests – holes in trees, made by the parents themselves or adopted as a home when birds like the cavities made by others
  • Simple scrapes – these are shallow depressions scratched out on the ground and they may be lined with materials or left to look like the rest of the surrounding ground
  • Cup-shaped nests – these structures are like small bowls and may be lined with materials like those used in nest box nests. They can be made of varied materials – swallows use mud while American robins and other birds use plant materials.
  • Platform nests – these nests are usually quite large and comprise large twigs and small branches
  • Plate nests are a bit similar to platform nests but much smaller and less organized; they may consist simply of a few twigs arranged in a shallow bundle
  • Pendant nests hang from branches.

When birds look for a cavity site, they may seek out a new spot on a tree trunk or investigate already existing cavities. These Eastern bluebirds (Sialia sialis) at Sandy Creek Park were examining one particular hole with interest, but a downy woodpecker was interested as well so there was some rivalry. The female bluebird chose to just sit on a nearby branch while her mate looked at the hole numerous times trying to make a decision.

    

Red-headed woodpeckers (Melanerpes erythrocephalus) excavate larger cavities in tree trunks to raise their broods. They may visit various trees before deciding on a spot.

      

Pileated woodpeckers (Hylatomus pileatus) may use the same holes year after year. They make holes for resting as well as for nesting and often include a “back door” so they can make a quick escape if a snake shows up.

          

Brown-headed nuthatches (Sitta pusilla), like this one at Jordan Lake, can be very industrious in excavating their nest cavities. You can watch them pecking away at the wood of a tree trunk or branch, scattering wood shavings and removing bigger bits of softened wood in their beaks to achieve a hole of the right depth for their babies. (See a short video of one at work here.)

   

I also saw nuthatches making nests on the edges of a farm and near the NC Botanical Garden. The pair working on a nest at the Garden were doing this with a great horned owl on a branch overhead, as well as a red-tailed hawk and crows who were raising a racket. Their presence didn’t bother the little birds; these nuthatches also appeared to have help from a previous year’s youngster willing to help the parents raise the new siblings.

 

 

    

Carolina chickadees (Poecile carolinensis) also dig out small holes in trees and snags.

      

Killdeer (Charadrius vociferous) use scrape nests which may look exactly like the surrounding area; their eggs then blend in really well with the environment and can be difficult to see.

When I first saw this nest suspended from a tree near a bridge, I had no idea which bird had built it. A birding friend had fortunately seen the parent bird fly to the nest – it belonged to a Northern parula like the one shown below (Setophaga americana).

    

I was lucky to see a female orchard oriole (Icterus spurius) collecting nice soft lining materials for its nest this past spring.

         

A red-winged blackbird (Agelaius phoeniceus) was doing the same with cattails – an obviously appropriate source for bird bedding!

       

Mourning doves (Zenaida macroura) and Northern mockingbirds (Mimus polyglottos) make fairly shallow, twiggy nests (“plate nests”). It makes you wonder if eggs ever roll out of them through cracks in the loose, low walls.

   

Many birds make cup nests and spend a good amount of time collecting the materials to produce them. Here you see American robins (Turdus migratorius) gathering grasses – they tend to fill their mouths as much as possible before flying off to the nest-in-the making.

      

Red-eyed vireos (Vireo olivaceus) will also attempt to get several pieces of bark into their beaks before flying back to the home site. The photos here are dark as the bird was deep in shrubs where little light was penetrating.

        

Blue grosbeaks (Passerina caerulea) weave what looks like a cross between a pendant nest and a cup nest; they also add man-made materials such as rags, cellophane, newspaper and bits of plastic.

    

Great blue herons and ospreys are builders of platform nests.The great blue herons (Ardea herodias) carry large twigs and branches to furnish a nest. At Sandy Creek Park they have been using the same tree-top platforms for several years now.

     

Last year, I saw this osprey pair (Pandion haliaetus) build their first nest from scratch; they weren’t enthusiastic about me being in the vicinity and would perch or fly overhead to give me “the evil eye” – sometimes calling to one another to sound the alert that they had spotted me down below.

 

 

This year, they were busy refurbishing the nest – these birds with longer-term mates may use the same nest year after year. Again, they would stop their work to stare me down.

 

The Acadian flycatcher (Empidonax virescens) makes a cup nest that is well-hidden among the leaves of the tree spot it chooses. A friend saw the pair constructing this nest and it was done by the time I visited. It seemed quite a tight fit for mom to sit in while brooding her eggs.

The bird whom I enjoy seeing most during nest construction is the blue-gray gnatcatcher (Polioptila caerulea). These little birds are very active and often don’t sit still for long as they feed in shrubs and trees. When they are busy making a new home though, they take their time to do a good job. First, they locate good locations for the materials they use – leaves, spider web to hold the leaves together and pieces of lichen to cover the outside walls.

      

They affix the lichen carefully to make a really beautiful, compact and elegant little cup. The female then sits in it and moves her body to ensure it gets the right shape and dimensions for her upcoming brooding.

     

The male and female both work hard on the nests and this year I got to see three pairs at work. In two cases, it was lucky I saw them flying to and fro because their nests blended in really well with the tree.

Unlike the cavity and platform nesters, the cup and pendant nesters usually need to build a new nest each year. At the end of the summer, for example, the blue-gray gnatcatcher nest had already deteriorated considerably with the rain and wind, even though it was a fairly calm and dry season.

 

Once the nest is complete, the avian parents brood and feed their babies before fledging and this will be the third part of this series. For now, I leave you with the male and female ospreys as they watch the birdwatcher….

  

Avian generations in the making – part 2A: nesting and man-made construction

Hi folks — today I’d like to share with you some of my observations on the second part of avian reproduction — the process in which birds make a nest and lay eggs. (By the way, if you look up “bird nesting” on the Internet, the search will lead you to a human activity: a shared custody arrangement where children reside in one house and the parents take turns living there with them. In the bird world, some avian parents will actually share a home, such as this very old and enormous sociable weaver nest (Philetairus socius) that I saw in Namibia.)

Females of a few species will deposit their eggs in the nests of another, such as some cuckoos and brown-headed cowbirds (Molothrus ater). Some people dislike cowbirds intensely because of their nest parasitism (the cowbird baby will hatch first and eat all the food or perhaps get rid of the other eggs or babies). I figure that this is how the cowbird evolved – it didn’t make a choice to wipe out other species so I can’t blame or hate the bird for it. But the cowbirds do appear to pick on particular species as involuntary “foster parents” and this may be affecting the success of the other species’ reproduction.

There are two general broad categories of bird nests – those located in or on man-made objects such as nest boxes, atop downspouts, in vehicles, in plant pots and other places and those constructed by birds in trees, shrubs and on the ground (i.e., the natural environment which I will discuss in the next blog so this doesn’t get too long!). When birds make a nest in a “human area”, people will often try to accommodate them, not using the object or vehicle or making the space safer. For example, when American robins (Turdus migratorius) put a nest on one of my downspouts, I covered the rainwater container underneath it so the fledglings wouldn’t drown when they leapt to freedom. (I did it just in time, too!)

Swallows and phoebes will also use human constructions as places to situate their homes. The cliff swallows (Petrochelidon pyrrhonota) gather up mud, making countless trips to wad up small balls of the material to carry back to a place like this pier at Cane Creek Reservoir where they line up their nests in a row.

   

Barn swallows (Hirundo rustica) locate their nests inside, using rafters to place a nest; they may end up sharing space with paper wasps and organ pipe mud dauber wasps (Trypoxylon politum), which doesn’t seem to bother them.

The Eastern phoebe (Sayornis phoebe) may use an inside corner of a patio overhang as a site that is conveniently accessible from outside.

Purple martins (Progne subis) living east of the Rocky Mountains almost exclusively nest in homes provided by people. The hanging gourd nests can be seen in fields but nowadays other types of plastic constructions are also used.

    

In order to attract barn owls (Tyto alba) back to areas where many traditional barns have been razed, people are also placing special boxes in fields with plenty of open space in front of them so that the owls will have a hunting territory adjacent to their front door. Made of heavy plastic, these boxes may be monitored by organized groups in an effort to document their use.

   

At the Mason Farm Biological Reserve, an eagle scout project involved bringing in cranes to attach very large nest boxes to the tops of trees for barred owls (Strix varia) – so far, I have only seen Eastern gray squirrels making use of these nests.

And then there are the nest boxes that people put up to attract Eastern bluebirds (Sialia sialis), brown-headed nuthatches (Sitta pusilla) and screech owls. In my yard, other birds use these boxes, too, including the Carolina chickadees (Poecile carolinensis) such as my one-legged,  banded friend Chantal, Carolina wrens (Thryothorus ludovicianus) who may puzzle about how to get a long twig into the box and house wrens (Troglodytes aedon), who pile up twigs in a rather untidy stack inside the box.

   

   

Chickadees construct lovely mossy nests lined with hair, fur or plant fibers.

      

The nuthatches have nests with bark strips.

    

Sometimes people will intervene when a nest is in danger. A Carolina wren put her nest into a boat at Cane Creek Reservoir that was rented out to people and keeping the nest there was not a good option as she would be missing her nest for hours when the boat was gone. The land manager was so kind as to relocate the nest into a tree right in front of the boat’s resting place; unfortunately, inclement weather caused the nest to dislodge that evening.

   

Another danger may also threaten the birds and their nests – predators. A friend and I found it unusual to see a tree swallow (Tachycineta bicolor) putting a nest in a bluebird box on the edges of a farm. Several days later, we saw a black rat snake (Pantherophis obsoletus) peering out of the box and the swallows were nowhere to be seen.

   

If you can manage to mount your boxes on poles rather than trees, put both squirrel and raccoon baffles on them and also place them away from overhanging branches, they should stay relatively safe from the squirrels, snakes and raccoons. Next up: birds’ nests with no human connections.

 

 

Avian generations in the making – part 1: courtship

The tragedies being faced in the Caribbean islands after hurricanes Maria, Jose and Irma are horrible and other than donate cash to help alleviate the needs, I’m not in a position to offer more assistance. I’m grateful for all those who can and hope government assistance will be forthcoming to help all the people in those nations recover.
The effects of the hurricanes also will be noticeable for the wildlife. Many of those living on land will drown or die of hunger; some birds may be a little luckier – able to shelter against the winds if they are native to a place or able to change their migratory pattern (e.g., delay arrival on wintering grounds) for a time. But when the effects of the storms are immense with lots of habitat destruction, the birds, too, will lack places to shelter and not have sufficient food supplies to survive.

It’s thought that some birds endemic to the islands may be severely endangered as a species. On 22 September, birders were happy to hear that eight Barbuda warblers (Setophaga subita) had been spotted on that island; not a lot but they may help ensure this tiny bird doesn’t become extinct.  At the time of writing this blog, the fate of some other bird species was still unknown. I hope that all the Caribbean bird species survive and will be thinking of them as I share this series with you on how birds take measures to ensure future generations. (It might seem odd to write this series now, but some birds are still feeding their young here.)

So, the process begins with courtship. Some birds mate for life, or at least form long-term (multiple-year) bonded relationships. They include bald eagles, black vultures, blue jays, Canada geese, white-breasted nuthatches, brown-headed nuthatches, Northern cardinals, Carolina chickadees, American crows, pileated woodpeckers and my favorite raptor shown above, the osprey (Pandion haliaetus).

Those who form ongoing bonds may have a courtship period that consists of the male bringing the female some food to indicate it’s time to get ready for nest-building. This was the case for these lovely Northern cardinals (Cardinalis cardinalis).

The American crow (Corvus brachyrhynchos) has a similar behavior; in my yard, I sometimes throw out bits of apple or bread for them in the spring as these seem to be considered real treats. The female will sit on a branch overhead calling until the male brings her some – and sometimes almost shoves it down her throat!

The Northern mockingbird (Mimus polyglottos) males will sing their repertoire in the spring to entice female mates – often they perch on the top of trees and fly up and down with spread wings in a beautiful display while singing.

        

   

The yellow-billed cuckoo (Coccyzus americanus) seeks new mates each year but has an interesting courtship behavior described by All About Birds: “A receptive female perches with its head up, pumping its tail slowly up and down…Just prior to mating, the male Yellow-Billed Cuckoo snaps off a short twig that he presents to the female as he perches on her back and leans over her shoulder. Both birds then grasp the twig as they copulate.”

 

     

 

The downy woodpecker (Picoides pubescens) females and males may both flutter between trees with slow wingbeats. Two females may also compete for the attention of a single male, a behavior I observed this past spring and which surprised me.

 

     

The male brown-headed cowbird (Molothrus ater) will vocalize for the female while spreading his wings in a display.

The killdeer (Charadrius vociferus) has a somewhat prettier courtship dance, bending forward and spreading its tail feathers to show off the colorful underside.

  

Next year, I hope to see more of the birds courting as it gives me a happy feeling.

The next step for the birds is nest-building. We don’t have the bowerbirds in North Carolina, who build elaborate nests as part of their courtship. But the species we have do spend a good deal of time on their nests and I’ll share some of their efforts in the next part of the series. (But one or two blogs on another topic will come first.)

 

Credit map: By Kmusser (Own work, all data from Vector Map.) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)%5D, via Wikimedia Commons

My nature muse and a delightful experience

Dear unseen spirit,

You are a muse for me who permeates the air and leaves and water and earth that form the sphere in which I feel so at home, at rest yet invigorated, excited, awed, happy and amazed in turn and sometimes simultaneously, in a welter of positive emotion and feeling.

Yesterday, you brought me one of those moments. A smallish, perhaps teenaged, painted turtle (Chrysemys picta), with a smooth ebony carapace with some iron oxide-like highlights, was busy laying her eggs. My friend Lucretia and I stopped to watch.

Lucretia had discovered her while walking a fence line near a lake cove, sticking to that border of mostly bare dirt except for some leaves and twigs so she could avoid the longish grass that could very well be harboring ticks and chiggers – the nemesis bugs for birders and naturalists!

 

Ms Turtle was not quite vertical but leaning like the Tower of Pisa with her bottom in a hole she’d dug and her red-striped front legs anchoring her above. She was using her back legs and toes to move aside dampened clay earth, sometimes moving her body side to side to widen the depression. We wondered how much she’d had to urinate to get the dry ground to a nice malleable consistency; it turns out that painted turtles can store water in their urinary bladder, which helps with buoyancy in the water – and nest digging on land.

When we first stopped, she withdrew her head into her shell and stayed motionless but not for longer than 45 seconds or so. Her natural impulse for self-protection was weaker than her need to procreate, so she resumed moving small mounds of earth.

After some 15 minutes or so, we moved on along the cove, Lucretia noting birds and me looking for dragonflies to photograph. Spring was still in the air with one female widow skimmer (Libellula luctuosa) being chased by 3 to 5 males in an aerial ballet as they sought to be the one who could grab her head and become her temporary mate.

One pair of conjoined dragonflies skimmed the water’s surface while others hovered over water plants or rested on shoreline foliage for a few minutes.

Spangled skimmer (Libellula cyanea)

  

Eastern amberwing (Perithemis tenera)   Halloween pennant (Celithemis eponina)

Thoughts of Ms Turtle came back to me and I cut my insect investigations short to go back around the cove to her birthing site. Lucretia was already there and waved me over – she’d just seen Ms Turtle expel two white eggs, which I saw below her tail as she resumed her back-leg maneuvering of damp earth. She was now covering the eggs and perhaps that is also what she had been doing when we arrived. Painted turtles lay from 1 to 11 eggs and we wondered if she had already laid some and was covering them in layers.

At any rate, she was now obviously done with placing her progeny in the nest and was filling in the hole. She deliberately and meticulously grasped balls of soft earth and maneuvered them over the eggs. Her instincts were good and she apparently was doing this all by feel as she couldn’t see what she was doing. Her back legs unerringly found the next clump to move into position and she was quite thorough in making sure it was placed and smoothed over in just the right spot.

The process was slow but careful and as she gathered in the mud, her body began going more and more horizontal – a really noticeable change from when we first saw her more or less standing on end to deposit her clutch.

Ms Turtle was no longer bothered by our presence at all – nothing was going to stop her completing the process, although she occasionally did pause for a moment or two. She’d been at this for at least 70 minutes or so – or perhaps longer if she’d already laid some eggs before our arrival. Lucretia commented on what a hard worker she was!

When Ms Turtle was finally entirely horizontal, resting on the packed earth that was even with its surroundings, she took one more precaution to prevent predators (e.g., snakes, chipmunks, squirrels, foxes, raccoons) from finding her developing offspring. She used her back legs to draw in leaves and twigs to top off the dirt over the nesting site so that it looked exactly like the surroundings!

This, too, was done deliberately and carefully and by feel – never once did she turn around to look at what she’d done. In fact, when she was finished, she set off at an angle to trundle rapidly through the grass to the lake, never casting an eye on the covered nest.

 

We vowed to investigate egg incubation times (on average, 72 days, making 19 August a possible hatching day) and Lucretia tied a paper towel on the fence in front of the site so we could re-locate it. I also tied some weeds into the mesh of the fence.

 

In the meantime, Ms Turtle was making good time to the lake and we saw her tip over the shoreline edge, only to end up on her back. Within 10 seconds, she’d righted herself and plopped into the water, briefly floating and then submerging.

 

 

  

   

We spoke about her wonderful work – even if instinctual, it was amazing to watch and we felt privileged to have borne witness to it. Suddenly, not far off-shore, up popped Ms Turtle; she floated at the water’s surface enjoying a well-earned rest after her double labors (birthing and excavation/reconstruction). Her carapace glistened and she was a beauty to see and admire.

It would be super to be able to see her hatchlings emerge in August. I don’t know if we will be so lucky but recalling their mother’s construction of a nursery will be a great nature memory for sure. And who knows what new event you, my nature muse, will bring along in the meantime – when I arrived home, two of the Eastern bluebird (Sialia sialis) had hatched!

Mother Nature, you always delight and/or edify to be sure!

Many thanks! Maria

                                 

Can you go home again? Apparently so!

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This year, I had the good fortune to see both brown-headed nuthatches (Sitta pusilla) and Eastern bluebirds (Sialia sialis) raise broods in some of my nest boxes. I saw the babies fledge, which was truly an enjoyable event.

 

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For some time, the parents continued feeding their babies after they left home, but eventually they got to the point that they could catch or find their own food. As summer progressed, the parents and children both visited my feeders and it was gratifying to see the families thrive. Then during September and October, I saw a behavior that I don’t remember from years past.

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The nuthatches started to return to their nest box almost daily. They didn’t check out nearby boxes but went to their original home and today they are still visiting there, sitting on top, fluttering around it and looking inside.

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Their frequent visits seem to have intrigued a local tufted titmouse (Baeolophus bicolor) who decided to take a look in their box, too,but that was only a one-time visit as far as I could see.

It’s not only the parents doing this, but also one or more of their offspring. So how true is the saying “you can never go home again” (origin a novel by Thomas Wolfe)? It originally meant that you can’t recapture exactly how things were in your youth because changes take place in situations and places. But people do often journey back to the places where they grew up and apparently birds do, too! Maybe they are wondering if their nest box is still the same good place for a home.

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The bluebirds began doing the same with their home nest box as well. They take turns flying from nearby branches to cling to the box and investigate the now empty dwelling. While the nuthatches just lean and peer inside, the bluebirds eventually go inside for a bit.

 

 

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Oddly, there seems to be some contention involved. For example, when this pair was investigating, they had a little tiff for some reason.

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I can only guess that the birds are checking out the nest boxes in anticipation of next year’s nesting season. The nuthatches and bluebirds will begin breeding again around March, although nuthatches might already begin building a new nest as early as December. It will also be interesting to see if they end up roosting in the boxes during the colder winter nights.

brown-headed-nuthatch-i77a4527-maria-de-bruyn-resWatching the nuthatches and bluebirds nest, fledge and feed is an enjoyable pastime and I’m looking forward to seeing them repeat the process next year. In the meantime, perhaps I’ll continue seeing them around the nest boxes this winter – as Pliny the Elder said, “Home is where the heart is” and something is sure attracting them back! (And yes, I know, that is a bit of anthropomorphizing.)