Hands-On Learning

     The Eastern Bluebird is a common species of open and semi-open habitats. Easily recognized by their brilliant blue plumage, bluebirds are a familiar sight in my Canton neighborhood, perch-hunting for insects from tree snags, mailbox poles and stonewalls.  

     My own yard not only provides excellent feeding opportunities, it provides bluebirds with a place to nest and raise young. In a typical breeding season, our lone nest box will produce two clutches of eggs.   

     After a successful first nesting this summer, a second attempt was soon underway. As activity inside the box increased, I confirmed that a new clutch of five eggs were placed. However, in the days to follow, the lively activity that had preceded the egg laying had all but ceased. Suspicious, I decided to check the box one more time. What I discovered was truly upsetting. The bluebirds had abandoned the nest box and five eggs due to a large infestation of sugar ants.

     Disappointed, I removed the nest and prepared the box for another possible nesting attempt. I brought the infested nest down to the woods to discard it properly and bury the eggs. As I was carefully picking out each individual bluebird egg to set it down on the ground, one of them had broken in my hand. The photograph below is what I found inside the broken egg.

     Admittedly knowing nothing about the development of an egg, I turned to the book; Manual of Ornithology (Noble Proctor and Patrick Lynch, 1993) for some enlightenment. I’d like to share with you some information from the book which helped me better understand the structure and development of an egg.

 

     The avian egg is a miracle of natural engineering. Light and strong, it provides everything a developing bird embryo needs from just after the ovum is fertilized until the chick hatches.

     The avian egg is a self-contained womb in which the embryo is protected and provided with the food and nutrients it needs to develop and hatch. But the egg is not a completely closed system, shutting off all outside contact. Birds, even as they are developing in the egg, are warm-blooded animals, with all of the metabolic activity that homoiothermy demands. The chick within the egg must be able to respire, to exchange gases and water vapor with the outside world, or it will suffocate.

     The bird egg must allow an efficient exchange of gases to support the growing chick, allowing waste gases out and oxygen in. The avian eggshell is not simply a coating of calcium carbonate but a complex laminate of mineral crystals embedded within a web-like matrix of material similar to collagen fibers. Reptiles, birds and mammals are called amniotes because the eggs of all three groups develop within an amniotic membrane. The amniotic membrane forms an enclosed, watery environment that protects the developing fetus and allows it to exchange gases with the surrounding world (Carey 1980, 1983; Romanoff and Romanoff 1949).

      The yolk of the egg supplies the embryo with nutrients, storing food until the chick hatches. The yolk sac surrounding the yolk is another embryonic membrane. The yolk is approximately 30 percent lipids (fats), 15 percent protein, and 55 percent water. Fat, not protein, is the primary food in bird eggs. This gives bird eggs a significant advantage over reptile eggs, in which the primary nutrients are stored as protein, because when broken down, fats yield more metabolic energy and water per unit than do proteins. They can thus survive in much drier environments than reptile eggs.   

     The age of the embryo, from what information I could gather, is anywhere between eight to twelve days old, given the size of the formed digit and toe plates.

     Despite the loss of our five bluebird eggs, I feel there is always a way to take a bad situation and extract something positive from it.  Learning about egg structure and the developing embryo was certainly an eye opening experience, as was the actual embryo in my hand.

     I also realized that I needed to be a better steward to the birds I provide for. Whether it be a hummingbird feeder or a nest box, periodic inspections and cleaning helps ensure a birds health and nest productivity.

     Finally, I would like to thank Noble Proctor and Patrick Lynch for publishing this outstanding book. The writing is excellent and easy to understand, and the drawings are exceptional.  Roger Tory Peterson’s foreword to the book says it best; “A gold mine of facts…Every library and biology department, as well as every birder, should have a copy close at hand.”  I couldn’t agree more.

Mob Mentality

     Red-tailed Hawks are one of the largest and most commonly seen species in Connecticut. The other morning while driving to the Riverside Park Sewage Pond in Hartford, I caught sight of one of these large raptors resting on a city lamp post. Perched beside the hawk was a Northern Mockingbird who was highly agitated and scolding loudly from a safe distance. Having failed to elicit a response, the mockingbird then embarked on an aerial assault which involved multiple pecks to the back of the hawks head and rump. In the end, the Red-tailed Hawk gave up and flew over to a nearby woodland, but not before enduring another strike from an angry Eastern Kingbird.

     So why are avian predators like hawks and owls always the recipient of another bird’s aggression? First and foremost, predatory birds provide a major threat to most other bird species, either because there is a good chance of being eaten or an even greater chance of having their young eaten. The behavior they exhibit is called "mobbing" and is done singly or in groups, depending on the species. For those who are not familiar with a bird’s mobbing behavior, it can be recognized by an array of harsh calls, wing fluttering and tail flicking.

     Mobbing occurs mostly during the height of the breeding season as a way to distract and encourage a predator to relocate to another area. Also referred to as the ‘move on’ hypothesis (Curio 1978), previous studies have confirmed that predators are profoundly distressed by mobbing and avoid the areas where they have been harassed. The ‘move on’ hypothesis appears to be most clearly linked to territoriality (Pavey and Smyth1998).  Learn more about territorial mobbing here;

http://www.fsl.orst.edu/flel/pdfs/Betts%20et%20al%202005%20Ethology.pdf

     As you can see from the photographs above, it can appear that predator harassment is risky business.  But in reality, birds who participate in mobbing are usually in very little danger. Species that are chosen to be mobbed are done so very carefully. For example, slow moving raptors like Red-tailed and Red-shouldered Hawks are less likely to strike back at an attacker, preferring to move on and save energy. Rarely would you see the same situation involve a Peregrine Falcon or Cooper’s Hawk.

Adult Cooper's Hawk in the same area two days later.
Where's the mockingbird now?

     Birders should also be aware of mobbing behavior during the winter months. On past Hartford Christmas Bird Counts, I have discovered Northern Saw-whet Owls in woodlands by following the scolding calls of Black-capped Chickadees and Tufted Titmice. David Allen Sibley writes in his book, The Sibley Guide to Bird Life and Behavior; Parids are social, bold, and inquisitive, traits that endear them to humans but make them among the most tenacious and aggressive songbirds when mobbing owls or other predators. Chickadees and titmice usually take the lead in announcing the presence of a small owl.

     Mobbing, on a rare occasion, can lead to dire consequences for the intended target. Winter flocks of American Crows often chase Red-tailed Hawks through city streets, forcing them into near-miss situations with telephone wires, buildings and even vehicles. Some, without a doubt, get injured or die as a result of these relentless attacks.

     Late last winter, I saw a Great Horned Owl get chased through the Cedar Hill Cemetery by a flock of very angry, noisy crows. When I finally caught up with the flock, the owl hung motionless by its neck, wedged between two branches. Did the owl make a mistake and stay out to long for another chance at a squirrel? If it did, it ended up costing the owl its life.  

Photo courtesy of Marcel Guerard

A Great Pond Pictorial Highlight

     Here are a few photographs I took of a Great Crested Flycatcher nest at Great Pond State Forest in Simsbury.

     The Great Crested Flycatcher is the only cavity-nesting flycatcher in North America. The nest hole is located in a dead tree stump along the edge of the pond, about five-feet from the ground.

     At the time these photographs were taken, both parents were actively catching dragonflies and feeding them to their lone nestling. Nestlings are often fed dragonflies, moths and butterflies without the wings removed.

     The Great Crested Flycatchers main winter range extends from southern Mexico, south throughout Central America, to eastern Panama.  

Signs Of Birds

     For those who enjoy watching birds, the hobby of birding can offer people many different avenues in which to pursue. More than just identification, birding involves everything from the study of various plumages, behaviors and habits, finding and documenting rarities, photography, hawk watching and banding.

     One such facet of birding I have recently discovered has been the art of recognizing bird tracks and sign. Every so often, there comes a time in the field where a dropped feather or an interesting foot print turns out to be a complete mystery.

     Some signs are quite obvious like the drilled sap wells of the Yellow-bellied Sapsucker. But others can be quite tricky. When those types of signs are encountered, birders will have to analyze each situation and look for clues to come up with the best possible explanation.  The more you observe and learn about the lives of birds, the easier it will become to interpret signs.    

     My first experience with avian forensics occurred years ago along the back trails of the West Hartford Reservoir. On an early morning hike, I happened upon the dismembered body of a red phase Eastern Screech-Owl. All that was left were two partial wings and a variety of other feathers, not much else. As I picked up the pieces to examine them more closely, I noticed that three of the feathers were different. After some careful home study, I had determined that the unidentified feathers belonged to an adult accipiter, most likely a Cooper’s Hawk.

     A more familiar sign in our woodlands are those that are left behind by the industrious woodpeckers. Of all the woodpeckers, the Yellow-bellied Sapsucker is the master of sign. The tell-tale sign of a sapsucker’s presence in an area is trees with multiple rows of holes drilled into the trunk. Even though I’m unable to locate their nest hole this summer, an active sap well in my Canton yard is a good indication there are sapsuckers nesting nearby.



Active Sap Well

     Another species that is frequently seen in my yard is the Pileated Woodpecker. Pileated Woodpeckers excavate large rectangular holes in mature trees as they search for grubs, beetles and ants. An enormous pile of wood chips below the hole is a sure sign of this woodpecker’s handiwork.  

     The largely nocturnal Great Horned Owl is often very hard to see. But a scattering of pellets under a stand of tall white pine trees may disclose a favored roost or hidden nest. Simply described, a pellet is a regurgitated mass of indigestible animal remains, comprised mainly of fur and small bones. People who study Great Horned Owls can often determine a bird’s present diet by the dissection of a pellet. They will also be able to gather information about the prey species itself, i.e. population size.

Weathered Great Horned Owl Pellet

     Bird tracks, or footprints, are a wonderful way to determine the presence and habits of a particular bird. The Spotted Sandpiper for example, is a common species whose track is found beside any freshwater body of water.  Before photographing its prints, I watched a hungry sandpiper delicately pick at the mud and chase insects along the banks of the Connecticut River in Wethersfield. A significant amount of track activity from this particular spot, both from the sandpiper and Killdeer, clearly shows an abundance of food here. Their occurrence in late June hints at nesting in the immediate area.

Spotted Sandpiper Tracks

     Winter is also an excellent time of year to look for bird sign. Not only is it simpler to find tracks in the snow, it is easier to discover nests from the past breeding season. The tree-top location of a Baltimore Oriole nest is unveiled as soon as every last leaf has fallen. Nearer to the ground, hard-to-find nests like that of a Chipping Sparrow and Common Yellowthroat allow birders to learn more about site locations and construction material.  

American Crow Track With Wing Impression

     One way to become familiar with track and sign is to study birds right in your own backyard. This is the place where you will know birds the best as well as the place you feel most comfortable in. Once you have achieved a close relationship with birds, it will become easier to identify their sign, even when they have long moved on.

Marsh Bird Relationships

     Station 43 in South Windsor is considered by many to be one of Connecticut’s premier birding locations. A beautiful eleven-acre marsh, Station 43 is owned by the Hartford Audubon Society and serves as one of the few breeding sites in the state for the elusive Least Bittern.

     On a hot, humid day in late June, I visited the marsh with hopes of catching a glimpse of this small heron. Like many of my past outings, achieving success with bitterns often entails a lot of patience as well as a bit of good luck. 

     As I eagerly anticipated the appearance of a Least Bittern, I couldn’t help but notice all the other wetland species flying about me. Swamp Sparrows, Marsh Wrens and Red-winged Blackbirds were all observed to be defending territory or actively nesting in a confined area of the marsh.  I thought to myself, how do all these birds breed in such close proximity, and still manage to be successful?

     Marshes are low-lying tracts of land that hold water throughout much of the year. They are dominated by thick, rooted vegetation such as cattails, bulrushes and sedges.  

     Birds that inhabit and nest in marshes are some of the least understood species amongst birdwatchers. The difficulty of entering an overgrown wetland in the summer is the probable cause for this. We know even less about the intricate relationships that play out within these lush habitats. My morning observations, though trivial, may shed light on some of those relationships.

     The first species that caught my attention was the Marsh Wren. Its lively song could easily be heard from the middle of the marsh. Since I couldn’t see the bird, I decided to use an ipod recording to help it come into view. Instead, the wren flew low and directly toward me. But before it could land, a Swamp Sparrow came out of nowhere and intercepted the wren, forcing it out of its territory. An agitated male Red-winged Blackbird also flew in to secure its boundary. 

     Marsh Wrens typically nest in isolated pairs, for good reason. This is because wrens are notorious for destroying the eggs and young of neighboring birds such as Red-winged Blackbirds, Swamp Sparrows, Virginia Rails, Sora, Least Bitterns and even other Marsh Wrens. The theory behind these destructive habits includes creating less competition for food with other marsh nesting birds and the expansion of their own breeding territory.

     Playing the Marsh Wren recording brought back memories of a time when I use to conduct call-back surveys for the Connecticut DEP in Glastonbury. I was always amazed at how fast a Virginia Rail could cross a marsh, on foot, when faced with a potential intruder. One rail I remember, parked itself at my feet for over a half-hour calling angrily. Sora is known to be even more aggressive than the Virginia Rail when it comes to defending its territory.

     The Red-winged Blackbird is by far the most conspicuous and energetic species at Station 43. Always in defense of their territorial boundaries, a minute never goes by without a chase or an aggressive response toward another bird. Here is nice description of the male and female blackbird’s territorial habits from the Birds of North America Online;   

     Male establishes and defends territory with clearly delineated boundaries during breeding season. Boundaries may shift within a breeding season (Dickinson and Lein 1987). All activities occur within territories, but male and female also forage, engage in sexual chases, seek extra-pair copulations, and prospect for other breeding opportunities outside territorial boundaries. Defense is based on conspicuousness, song and visual display, and aggressive responses to persistent trespassers (Nero 1956b, Orians and Christman 1968, Peek 1972).

     Existence of female territoriality is controversial. Female is aggressive toward others. Some authors (Nero 1956b, Beletsky 1983a, Hurly and Robertson 1984) assert that females defend “subterritories” within territories of males, but female display perches overlap extensively (Searcy 1986) and the primary aggressive vocalization (teer song) does not deter other females from settling (Yasukawa 1990). Nests are not overdispersed, as would be expected if females were territorial (Picman et al. 1988, Yasukawa et al. 1992a). Dominance status of resident female depends on order of settlement and distance from nest when interacting with other females on male’s territory

     As for my morning search for Least Bitterns, I did finally locate a single bird clinging to an alder bush. Many birders, including myself, raised concerns about the absence of bitterns this spring. Were they no longer breeding at Station 43? What I found out about this year’s late discovery is provided here, courtesy of BoNAO; 

     Because Least Bitterns are highly insectivorous, delayed breeding cycle may be a response to the life cycles of aquatic prey. Emergence of aquatic insects in temperate-zone wetlands peaks in Jun (Orians 1980) when these bitterns are feeding young. Later broods not definitively known, but temporal pattern of nest initiation suggests double-brooding may occur (Kent 1951, Weller 1961). If so, late Jun to mid-Jul in Iowa, with second broods larger than first, owing to the increased availability of food later in the breeding season (Weller 1961).

     In addition to the increased availability of food, I’d like to suggest another benefit to delayed breeding. A delay could help bitterns avoid other nesting birds at a time when they are the most aggressive. A toned down wren or blackbird may be preoccupied with feeding nestlings, rather than territory expansion. This might be enough to reduce the chances of egg loss. 

     Despite all the known conflicts associated with nesting in a marsh, there are a number of important advantages. First, situating nests in and above submerged vegetation helps protect eggs and nestlings from land-dwelling predators like raccoons. Nesting among Red-winged Blackbirds provides additional protection for birds against avian predators such as Blue Jays and Common Grackles.The abundance of aquatic prey that surrounds the nest site is essential to feeding fast growing young.

     If I had to pick one word to describe the relationship between marsh nesting birds, it would have to be tenuous. Even though I singled out the aggressive breeding nature of both the Marsh Wren and Red-winged Blackbird, it is important to realize that each and every wetland species is fully capable of defending its territory, invading nests and destroying eggs to further their own breeding success.

Bank Swallow Nest Colony

     The Bank Swallow is a common and localized breeder in the state of Connecticut. With their darting flight, they are often seen over larger rivers, feeding frantically on flying insects. Unfortunately for many of us, this is typically the only way we ever get to enjoy these small, brownish birds.

     Early one morning, while birding in the Hartford North Meadows, I caught sight of a flock of Bank Swallows feeding over an inlet alongside the Connecticut River. As I sat and admired their incredible aerial pursuits, I noticed that most of the swallows were moving inland, rather than toward the river.

     Curious, I made it a point to follow their movements and see exactly where they were heading. My curiosity eventually led me to a sand and gravel pit adjacent to the meadows. After a few minutes of diligent searching and skirting dump trucks, I was thrilled to have discovered a colony of Bank Swallow high upon a large mound of dirt.  

     Bank Swallows, as their name implies, use vertical banks along rivers to dig nest burrows. If available, Bank Swallows will also make use of artificial sites such as sand quarries and road-cut banks. Both of these sites allow swallows to easily excavate burrows into eroding and loosened soils. 

Bank Swallow excavating burrow

     Recognizing that this was a unique opportunity, I decided to spend some extended time with the North Meadows colony. From the cover of my car, I was able get up close and personal with these birds.

     Interesting behaviors at the nest colony included a variety of physical interactions. Constant fighting over nest holes and mates often resulted in pairs fluttering toward the ground, pecking at each other. Vocal threats and pushes also ensued when intruders mistakenly entered wrong burrows.

     Another form of behavior I observed involved the excavation of a nest burrow. At two of the nest holes, dirt was briefly seen being forced out of the entrance tunnel by use of the swallow’s feet.  A more thorough explanation of this and other burrow-digging techniques is provided here from the pages of The Birds of North America Online.

   Bank Swallows have smaller, more conical bills, and a proportionately larger cucullaris-lateral rectus muscle complex than other swallows (Gaunt 1965). Burrows are dug with the bill, feet, and wings (Stoner 1936) as birds cling to a slight projection on the bank face, and dig using their bill in a rapid, slashing motion and feet in a scratching motion. Dislodged material from inside the burrow is ejected with vigorous kicks and wriggling body and wing shuffling movements. Burrows are excavated by groups of individuals, and excavation tends to be clustered in colony so that breeding is synchronized within sections (Hoogland and Sherman 1976, Freer 1977, Sieber 1980).

     Once a burrow is completed, the terminal end (chamber) is slightly enlarged upwards and to the sides. The nest chamber floor is constructed to be level with the burrow floor. Bank Swallow nest material includes plant stems, grasses, rootlets and leaves. Clutch size ranges from two to seven eggs.  

     As important as it is for Bank Swallows to find suitable nesting surfaces, it is equally important for the swallows to have prime foraging habitat surrounding the colony. Foraging occurs widely over most open lowland habitats such as agricultural areas, wetlands, grasslands and rivers.

Weather Related "Groundings"

     In the birding world, spring migration is the most anticipated event of the year. As the temperatures rise, so does a birder’s enthusiasm to find new migrants. Picture perfect days often bring out the masses to well –known Connecticut hotspots like Hammonassett Beach State Park in Madison and Milford Point.

   Still, picture perfect days in the spring can sometimes be hard to come by. April showers bring May flowers, but it might also bring fog, wind and downpours too. These unsettled days are almost always avoided by the average birdwatcher, but not me, I prefer them.

     As a primarily inland birder, I rely heavily on weather systems to drop and delay birds that would otherwise bypass my region. For example, Red-throated Loons, White-winged Scoters and Horned Grebes are practically guaranteed to be found along the Connecticut coast during the appropriate time of year. But in Hartford County, those same species are nearly impossible to find without the assistance of foul weather.

     So how does a person who lives far away from the coast find these uncommon species? To start with, you need to keep your eye on the week’s weather forecast.  If the forecast calls for precipitation to move in during the overnight, an effort should be made the following morning to search reservoirs and lakes for grounded migrants. Secondly, dedicating yourself to a favorite location will help prevent hard-to-find species from going undetected. Persistence will eventually reap rewards.

     Batterson Park Pond in Farmington is one place I continue to check on a regular basis. Conveniently located on my way to work, this 140-acre body of water has been a pleasant surprise over the years. Last April’s weather related sightings at Batterson Pond included Lesser Scaup, Surf Scoters, Red-breasted Merganser, Horned Grebe, Red-necked Grebes and Common Loons. 


Batterson Pond in the fog and rain

     The same rules can also apply to finding migrant shorebirds. When inclement weather is encountered, shorebirds will often seek refuge within farmland or along lakeshores until migratory conditions improve. Black-bellied Plover, Sanderling, Dunlin and Short-billed Dowitcher are some of the prized inland finds.

     Clearly there are many benefits to birding inland during unsettled weather. Along with all the excitement of finding loons, grebes and shorebirds, comes the intimate encounter’s with birds that may be difficult to obtain from a coastal site.

     The next time a bit of rain cancels you’re birding plans, you might want to think twice about staying indoors. Who knows, there could possibly be a flock of ten Red-necked Grebe resting on a small pond near you!