Bluebird Boxes Offer insight Into Bird Behavior

The male Bluebird checks out one of our Bluebird Boxes

I started to clean out the nature preserve’s Bluebird Boxes last week. The calendar told me it was time to do it, even if the weather didn't quite agree. In fact, there was an impressive snow squall taking place when I did the boxes in our largest field. Despite that, a pair of bluebirds stayed nearby – the male was singing and both birds were checking out one of the boxes only minutes after I had cleaned it.

The female bluebird  warns off a swallow that shows interest in her box

Cleaning boxes probably sounds like a mundane task, but I actually look forward to it. I get to examine the nest designs of well over one hundred bird architects. Primarily, the builders belong to just a handful of species, but individual birds belonging to the same species can have their own unique style.

The male Bluebird preens as the female checks the suitability of a nestbox 

An extremely feathery Tree Swallow nest freshly removed from one of the boxes

Tree Swallow nests are the type most commonly found in our boxes, and these nests are most often decorated with feathers from other birds. Some swallows only make use of a few feathers, while some go all out and use dozens of them. All feathers are not equal to the Tree Swallow – some types are ascribed much greater value. Although they must be difficult to come by, white feathers seem to be especially prized, and it seems as though Tree Swallows must put some considerable effort into obtaining them. The majority of the white feathers that I found in the nest boxes this time belonged to Ruffed Grouse – a bird that incidentally, is not known for its white plumage. The whitish feathers come from the grouse’s underside. 

 

Feathers of Cedar Waxwing, Blue Jay and grouse decorated the nest in this box 

The tip of the Cedar Waxwing feather shows a red waxy projection

So an interesting thing about Tree Swallow nest is how they can help you determine some of the other bird species that are residing in a given area. This time, the feathers of over one dozen bird species were found in the nests, included those of Wood Duck, Cedar Waxwing, Blue Jay, Red-tailed Hawk and Cardinal. Other birds incorporate feathers into their nest designs, but they don’t usually do it with the same panache that characterizes the Tree Swallow’s efforts. House Sparrow and House Wren commonly use nest boxes, and both species will sometimes use feathers. The latter species uses feathers much in the same way it uses twigs – just as building materials and not as decoration or insulation. One of the wren nests I looked at the other day had about a dozen bluebird and cardinal feathers enmeshed in its twiggy support structure. I recall once a Screech Owl that had a similar gaudy collection of feathers on the floor of its nest box, but in that case it was Blue jay and Cardinal feathers. At the time I surmised that feathers came from birds that the owl had eaten.

 

Beneath the Tree Swallow nest was a Bluebird nest with an egg still in it

A House Wren jammed this box completely full of twigs

Often more than one nest will be found in a single box – representing the use and reuse of a box by multiple pairs of birds in a single season. Typically, there would be a Tree Swallow nest or a Bluebird nest on the bottom level, with a Wren nest or a House Sparrow nest build on top of it. In some cases, possible foul play is indicated. In one instance, I suspected that the lower nest was still being used when the new owners came to claim the house. For beneath the Tree Swallow nest, I found a bluebird nest with an egg still in it. Now did the Bluebird abandon the nest before the swallows decided to move in, or were they driven out?

 

Long after young  fledged from this swallow nest, a mouse used it  for a place to cache seeds

This mouse nest was built on top of a Chickadee nest - note the green moss from the Chickadee layer

This mouse nest is made mostly from cattail down and grass

Mouse nests (most often  belonging to the White-footed Mouse), are often found in our Bluebird boxes. The mice move into the boxes in the fall and there they remain to raise at least one brood during the winter. Last winter a large proportion of our boxes held mouse nests, but not this year. This time only 20 or so boxes hosted nests and most of those were  already abandoned by the mice by the time I came by. Whenever I find an active mouse nest, I of course, leave it alone and allow the mice to finish their breeding cycle before removing it. 

This mouse nest is made almost entirely from bitten off pieces of milkweed silk

Blackbird Fallout and a Rare Yellow-headed Visitor

Our blackbird flocks are composed mostly of Red-winged Blackbirds and Common Grackles

The weather has remained decidedly winter-like in the Northeast, and this is leading returning flocks of blackbirds to remain concentrated in good habitat areas throughout the region. Marshes can be especially good places to find these mixed flocks of Red-winged Blackbirds, Common Grackles and Cowbirds, but nature preserves like ours with bird-feeding stations can also become major blackbird havens.

The flocks very efficiently glean the ground around the bird feeders for edible morsels

At the nature preserve many hundreds of blackbirds have been descending on the bird feeders and to a large degree displacing our usual patrons – including the Cardinals, Mourning Doves and sparrows. The vast majority of the blackbird flock is composed of male Red-winged Blackbirds and that species’ boisterous calls contribute most to the incredible din that the flocks generate. Typically the male Red-wings come north before the females; they do this in order to make an early claim on the best breeding territories.

The blackbirds have somewhat displaced many of our other winter patrons

Blackbird flocks move with a good degree of synchronization, even though their flight formations tends to be looser then that of waxwings or starlings. The blackbird flocks fly low over terrain, and their large flocks can be extremely long – sometimes even stretching from horizon to horizon.

A male Red-winged Blackbird sits upright and starts to show his red wing feathers

Cowbirds make up a smaller proportion of our blackbird flocks

In the early morning, just after the sun rises, the flocks arrive at the preserve and land in the trees around the feeding stations. When all looks safe and secure on the ground, a few brave individuals fly down and start to feed. When it’s clear to all that these pioneers were not snapped up by monsters, the rest begin to descend – but only few dozen at a time, until the entire flock is down and feeding. A feeding flock is intensely skittish, and if any individual in their group gives the signal (which as far as I can determine, is imperceptible to an observer), the flock simultaneously takes flight with a percussive “whoosh” sound. After this they usually gather in the trees above the feeders again, but sometimes the flock will go further, and even leave the general area.

The Common Grackle has an iridescent blue and purple head - hard to see during a snow squall

Some Grackles have a taste for the suet

However, this never lasts long, and soon enough the flock is back in all its glory. The sound of many hundreds of blackbirds simultaneously calling is pretty overwhelming, and to me, it is the first true indication of spring. When there is a break in the weather and when the snow and ice melt on the breeding grounds, these large flocks will break up and the birds will begin staking their territorial claims. But if the winter weather makes a comeback, the flocks are quickly reconstituted and they return to the winter feeding areas. 

A male Yellow-headed Blackbird (a rarity for our region) probes with its bill into the seed husks

At my yard feeders last week we picked a rare visitor out of our own mixed blackbird flock. It was a male Yellow-headed Blackbird – a species that breeds in the far west and winters in Mexico and the extreme southwestern US. This species shows up in the Northeast only by accident. For us, the bird was easy to pick out of the moving flock. Its bright yellow hood and large white wing patch were very distinctive markings, but on the ground, among the throngs of mostly Grackles and Red-wings, the bird was surprisingly difficult to locate. This was due to its feeding behavior. When looking for seeds the Yellow-headed Blackbird would have its face pressed right to the ground – with its beak probing into the snow, and this effectively concealed its yellow front. Also, the bird’s white wing patch is not so evident when it’s not flying or displaying.

The Yellow-headed Blackbird - continuing to feed during an intense snow squall

When feeding the Yellow-headed Blackbird would usually hold its tail high, and at a noticeably more extreme angle than the Red-wings do. So in order to locate the bird, we would look for the one tail that was sticking almost straight up. The Yellow-headed Blackbird remained with us for 2 days, and then a short thaw prompted the flock to move on or disperse. In subsequent days, after winter had reasserted itself, the blackbird flock reassembled at the feeders, but this time there was no Yellow-head in their ranks. Hopefully, he has realized his mistake and is making his way back west.

The Return of the Resident Geese

Our resident Canada Goose pair - Greta and Felix first nested here in 2005

Birds have begun to return now at the nature preserve – the blackbirds, Killdeer, and even a Woodcock was recently spotted. Our original resident pair of Canada Geese came back early last week and were seen on one of the beaver ponds quite close to their traditional nest site.

Greta does all the incubation, but Felix stands guard much of the time

When Greta leaves the nest to feed, she covers up the eggs with her own down feathers

This pair, named Greta and Felix, first nested here in 2005, and every year since, with the exception of last year, they successfully produced goslings. In 2012 the beavers had raised the level of the pond and the so the birds' favorite nest island was submerged. This compelled the Geese to build their nest in a new and less secure location. 

Greta turns her eggs so they incubate evenly

Hatch day arrived (circa 2011)

Last year, the fallback nest site was located just beneath one of the beaver dams. As I've mentioned before on this blog, beaver dams act like wildlife highways, and it was only a matter of time before some egg-thief came upon the nest. Sure enough, just one day after I discovered where the goose nest was, some predator also found it, and the eggs were pilfered.

7 goslings hatched on the nest island (circa 2008)

Felix leading the brood across the beaver pond

This wasn't the only tragedy that the pair had experienced – in 2007, an enterprising raccoon took advantage of on overhanging tree to reach the nest island and ate or damaged all but 2 of the eggs in the nest. The geese, as formidable as they seem to us, weren't able to drive the masked intruder away and had pretty much given up even trying by the time I got to the scene. I was drawn there by the mournful honking of Greta, as she helplessly watched the raccoon at work. That year the geese only produced 2 goslings, but they managed to raise both of them to the point of fledging.

The unhatched eggs remained in the nest for weeks until some animal finally discovered them (2010)

In 2010 and 2011, Greta produced an entire clutch of eggs – 7 or 8, but in both years only 2 of the eggs hatched. In 2010, after the 2 goslings were able to leave the nest island with their father, Greta kept returning to resume incubating the unhatched eggs. Finally, her duty to help protect the new goslings broke her attachment to the nest and the remaining eggs were abandoned.

Each year in spring, one of our foot trails becomes the "goose trail" once the young birds are ambulatory. At least 4 times a day, the parent geese escort their charge several hundred yards overland between the beaver pond system and the man-made pond. Often in the late spring and early summer, pedestrian traffic will need to stop and pull way off the side of the trail to allow the skittish family to pass by.

Taking the kids on the overland route (circa 2010)

Other pairs of geese have nested at the preserve, and a few have nested somewhere beyond our boundaries, but then traveled here to finish raising their broods. Greta, Felix and their young were always the dominant birds and they would persistently claim the prime feeding areas as well as the best nesting place. Mostly Felix would be responsible for chasing other geese off, but occasionally Greta and goslings would join in.

Just another day of hissing at the beavers 

Felix chases after Julia - who doesn't really offer much of a reaction.

In 2010, the goose family suddenly decided that they loved apple pieces and they started vying with the beavers to get some of theirs. They already were known for hissing and charging at beavers when they swam to close to the goslings, but now competition for apples brought these 2 disparate families into contention even more often. The beavers seemed to be losing the competition –that is until they came up with a great technique to unsettle the geese. I coined this “Goose-tipping” –and it entailed a beaver swimming directly below a goose, and actually making gentle contact with the bird’s feet. This would immediate cause the goose to beat a hasty retreat and thus leave the beavers to enjoy their apples in peace - for a little while, anyway.

The goslings are beginning to molt into adult plumage

Normally when Greta and Felix return in the late winter they bring with them their adult-sized young from the previous season. This was not the case this year because of the nest failure in 2012, but in other years, the yearling geese were tolerated by their parents only until nesting began, and then they would be unceremoniously chased off. However, Felix does seem to be mellowing with age, and he seemed to not be quite as vigilant in his efforts to run off the old kids in the last several years.

Greta & Felix and the rest of the geese that failed to reproduce in 2012 - gathered together for a group picture

With the beaver’s lack of attention to the dam at Morton’s Pond (the first beaver pond), it looks like the old goose island will be well above the water line this season, and ready to once again become the nesting place for our most faithful pair of resident geese.

Rabbit Friends and Bohemian Fallout

The Rabbit that recently befriended me - and he's not invisible and his name isn't Harvey

Over the years quite a few nature preserve denizens have become acclimated to me  - enough so that they allow a close approach. For whatever reason, few of these have been rabbits. With the notable exception of a Snowshoe Hair that once made a careful inspection of my shoe, the only rabbit that has really befriended me has been an Eastern Cottontail that I call Trés. And yes, he actually likes his name.

Trés' split ear distinguishes him from all others in the hopping crowd

He casually comes right up to me and asks for some sunflower seeds

A few months ago, when Trés first hopped up to me, I thought he was sick, and therefore unlikely to last very long in the predator rich environment of the preserve. I considered bringing him to a wildlife rehabilitator, but after watching his behavior for several days, I determined that his only disorder was excessive friendliness to me (hopefully, this isn't a terminal condition.) In fact, he acted normally in all other respects, and he demonstrated that he was quite capable of running away and concealing himself when he had to.

The Snowshoe Hair that once inspected my boot

The secret to winning Trés' trust was my handy bag of sunflower seed, which I carry primarily for chickadees. Truthfully, I never actively tried to befriend him. No, it just happens that 2 of the fence posts where I regularly leave the seed are in his territory, and so now, just like dozens of his winged compatriots,  he eagerly awaits my arrival, and for me to hand over the treats. 

Just a small portion of the Bohemian Waxwing flock that visited us last week

An amazing flock of Bohemians Waxwings visited the nature preserve several times last week. As the week progressed, their numbers "waxed" until the flock was 350 birds strong. A flock of Bohemians of this size resembles in many ways a flock of European Starlings. The flock’s tight formation assumes a globular shape, which undulates in waves as it moves through the air – and looks almost like a shape-shifting amoeba or a swarm of bees.

These birds show many colorful spots on their wings and tails

From the back, the Bohemian's yellow edged wing feathers create an interesting pattern

Bohemian Waxwings make a distinctive purring trill as they fly – and when the flock is this big, it sounds more like they are sizzling. Many days last week brought strong wind as well as snow and ice. Though 30 mile-per hour winds were enough to ground most of the preserves avian population, it wasn't enough to discourage the Bohemians from taking to the air. In fact they seemed completely unperturbed by whatever the weather dished out. Indeed, even with the high wind they navigated a circuit through the preserve without much difficulty. I guess it's pretty much what you’d expect of birds that only rarely leave the latitudes of the far Northwest, where weather like this is pretty typical.

Underneath their tail is a prominent patch of bright cinnamon  

I resolved to try to get some decent quality video of them. And last week probably represented my best chance, but again I was unsuccessful. The truth is that these birds seemed to be deliberately taunting me! Damn those beauties!! They would be feeding on buckthorn berries in one area – I would set out after them with the better (and much heavier) camera, but when I returned to the spot where they were only minutes before, they would be gone. I’d then see them perched on another distant tree top, but by the time I made it over to them, they’d take flight again and move back another few hundred yards. I wouldn't take this too personally – if it didn't happen so many times!

One day, I deemed it far too windy for me to even try to get close to them with the better camera. Instead, carrying only my tiny camera, I did manage to keep up with the flock as it hopscotched around the preserve. I kept company with them for about an hour while they made the rounds of our (mostly barren) fruit trees. For the most part they were visiting buckthorn trees to partake of that tree’s bitter dark berries. Their mode of operation entailed landing in the crown of a tall tree right above a fruit laden buckthorn – and then, a few birds at a time, they’d descend to the berry tree, until about half the flock was engaged in something like a low intensity feeding frenzy – I mean, they are waxwings and not piranha.

Robins and Cedar Waxwings also partake of the buckthorn berries

There are almost always at least a  few Cedar Waxwings mixed in with the Bohemians

The feeding behavior (as well as the nomadic behavior) of these birds is decidedly finch-like. In fact some birder-folk refer to Bohemian Waxwings as “honorary” finches for this reason. Like crossbills, they sometimes hang upside-down and flutter their wings when they feed on berries, seeds or buds. Their colorful feathers are most on display when feeding in this manner, as the inverted birds flagrantly show off the bright cinnamon colored patches underneath their tails. The bright yellow, red and white markings on their wing feathers are more visible when feeding like this.   

Beavers at May Pond and Their Unwelcome Scavenging Visitors

Beavers emerge from a hole in the ice at May Pond

Our Beaver colony continues to reside at May Pond, more than a month after the dam collapse at Secret Pond forced them to abandon their main lodge and winter food supply. But despite their hardships, all 7 beavers look well and appear to be healthy.

 A one year-old kit peels bark off of a poplar branch

Since the disaster, I've been providing them with emergency rations, and that seems to be enough for them to keep body and soul together. It has been a bit of a mystery why they haven’t been trying to retrieve more food for themselves – either from the fields or from the exposed food caches at Secret Pond, but the answer to that may have to do with the increased amount of predator activity around the nature preserve this winter – as I've written about in several recent blog posts.

Julia sits in the shallows and enjoys some willow twigs

This unsettling reality was quite literally brought home to the beavers this week when a raccoon died on top of the dam at May Pond, and a procession of carnivores turned up to claim their share of the carcass. I discovered the unfortunate deceased animal after I followed the tracks of a Fisher in the vicinity of Secret Pond. The tracks lead me to a nearly inaccessible portion of the May Pond dam.

Next to the dam, Julia and Blueberry pull strips of bark off of a log

On top of the dam, the footprints of no less than a half dozen predators and scavengers converged on the frozen and almost unrecognizable carcass of the raccoon. I initially thought that I could move the raccoon to a place where its popularity wouldn't be the cause of such consternation for the beavers, but I soon found that it was frozen tight to the dam - and it wasn't going anywhere. I thought it unlikely that I’d be able to dislodge it without taking a chunk of the dam along with it.

 Muskrats are far more vulnerable to the predators than Beavers

I decided to set up my trail camera up on the dam so I could see who exactly was putting the beaver’s nerves on edge. Even under normal conditions, a beaver dam serves as kind of a wildlife highway, but the added allure of a dead animal, turned it into a major thoroughfare. It's important to note, that though the presence of these predators may be upsetting to the beavers, none of them normally present any real threat to an adult beaver. An adult beaver easily out-weighs any of the carnivores that share their habitat at the nature preserve.

A one year-old kit climbs onto the ice to bust it down and enlarge the ice hole

The Crows were the first to be captured on video. A flock of 20 or more took turns tugging away at bits of the frozen carcass. A few arguments took place between them, but for the most part, the crows were good about taking turns and sharing.

Crows gather around the dead raccoon during the day time

An adult Red-tailed Hawk keeps its wings and tail spread out over its discovered feast

The next visitor – also by day, was an adult Red-tailed Hawk. This hawk probably had to fend off crows in order to get his turn, because the camera captures him striking a very aggressive posture. He hunches over his prize with wings and tail feathers spread – looking as large and formidable as possible, while at the same time covering from view as much of the carcass as he could. The camera’s microphone captured him voicing shrill warnings to all potential interlopers.

A Gray Fox comes to take its share well after dark

The fox stays alert during the entire time it spends with the carcass 

At around midnight, a Gray Fox visited the carcass and spent some time prying away at frozen bits of it. The fox stayed alert during the entire time and frequently looked up from his task to scan the darkness for other scavengers. At one point, the fox hears something, which causes him to spring to attention and to bolt over the dam in the opposite direction.

The Fisher shows up on the scene in the early morning hours 

About an hour later, the Fisher showed up and spent at least 10 minutes working on the carcass. This remarkably muscular animal is quite adept at pulling and prying off chunks. Although he remained aware of what was happening around him, he didn't seem as nervous about being there as the fox did.

The fisher feeds apparently unperturbed by any hungry competitors possibly lurking in the dark

Sensing the potential danger, the beavers were inactive for 2 successive nights. I know this mostly because they weren't captured on video, nor were their footprints found on the dam. However, on the 3rd night at least one of them did come by the carcass. On the video, an adult beaver leisurely walks through twice; I’m not sure which beaver it was since the camera didn't trigger until the beaver’s tail was just disappearing over the dam and into the water.

A raccoon with a bob-tail walks over the dam several times, showing understandable caution

2 nights in a row, a raccoon with a very short tail came by the carcass and briefly sniffed around the vicinity of the dam. This raccoon seemed justifiably concerned about what was happening here. Perhaps this is a relative or the mate of the one that died?