Jul 062018
 

Flocking provides many benefits but questions remain

“How early in the year it begins to be late” Henry David Thoreau

Nature plays a cruel joke on us in early July. Just as summer is getting started, intimations of autumn can already be seen. One such sign is the formation of flocks in some birds. In the city, large congregations of European starlings will soon be roosting in shade trees and advertising their presence by their clamorous calls and frequent flights from one tree to the next. In local wetlands, red‑winged blackbirds are flocking up and, by mid‑July, swallows will start to congregate on wires, especially around farms.

Swallows on wire in post-breeding flock – Wikimedia

A flock of ring-billed and Bonaparte’s gulls at Hillman Marsh near Point Pelee National Park – Drew Monkman

 

 

 

 

 

 

 

 

Advantages of flocking

Flocking confers a number of advantages to birds. First, there is safety in numbers. By flocking together, the chance of any one individual being killed by a predator is lower than if the bird was by itself. With so many eyes watching, it is likely that at least some of the flock members will spot an approaching predator while other birds are busy feeding, sleeping or simply looking in the wrong direction. When predators attack a flock, they try to single out a bird on the edge of the group to pursue. However, once in flight, most flocks change shape constantly and both expand and contract in size. This makes it very difficult for the predator to remain focused on one bird. There is also evidence that it may be physically dangerous for a predator ‑ which may not be that much larger than the prey species it’s pursuing ‑ to dive into the middle of a fast flying mass of birds.

Flocking can also provide better access to food. After spending the night together in a communal roost, it is thought that birds gain information about good feeding resources by following older, more experienced individuals when they fly off to feed. This becomes especially important in the fall when food is erratically distributed and cooler weather, along with the demands of the approaching southward migration, mean energy requirements are higher.

Scientists have often wondered why older birds would want to share food information and potentially end up eating less themselves. It appears there is a worthwhile trade-off. In several species, it has been shown that older birds, being more dominant, actually appropriate the safest, most central locations in the roost while the younger, weaker birds are relegated to the edges. This exposes the less dominant birds to a greater danger of predation. The arrangement is advantageous for both groups ‑ older and stronger birds allow their weaker brethren to bear the brunt of predation while younger and weaker birds get to follow the others to good foraging sites.

Flocking also enables birds to expend less energy in flight. When the lead bird flaps its wings, it creates uplift for the birds behind. Each bird (except the leader) is flying in the up wash from the wing of the bird in front. This enables the flock to use less energy and reduces fatigue.

Mobbing and pishing

Although not technically flocks, birds will also congregate together to attack, chase or simply pester a predator. This is usually done to protect offspring. Known as ‘mobbing’, the behaviour includes flying around the intruder, dive bombing and calling or squawking loudly. The loud alarm calls also serve to summon nearby individuals to join the attack and drive the predator away. Mobbing is especially noticeable in crows, which can often be seen and heard pestering a cat, fox, owl or other predator.

A crow harrassing a Red-tailed Hawk in Peterborough – Helen and Larry Keller

 

 

 

 

 

 

 

Although mobbing may involve some risks, there are obviously benefits. All of the birds in the mob increase their chances of survival and reproduction. An individual on its own, however, would stand little chance against a predator. There is also research showing that crows may even place sentinels in trees to watch for possible predators. This is done so that other nearby crows can safely feed on the ground. When the sentinels start calling loudly, the feeding crows will either fly off or begin to mob the intruder. Don Finigan of Peterborough told me recently about a fox that makes regular visits to his yard to hunt squirrels. Each time, the fox’s arrival is announced by the raucous displeasure of the crows.

The mobbing reflex on the part of some birds explains the effectiveness of a birding technique known as ‘pishing’. It is used to bring birds in closer for better views. The raspy, rough quality of the pish sound birders make is similar to the alarm or scolding calls of small songbirds such as chickadees. Scientists believe that birds interpret the sound as that of another bird that has discovered a predator and is recruiting help. An alternative explanation is that some species of birds are simply curious and have evolved to investigate unknown noises.

To pish, choose a place where there is already some bird activity such as the calls of chickadees. Place yourself close to some trees or shrubs where the birds you attract can land. Pucker your lips and make a loud, forceful “shhhh” sound, while tacking a “p” on at the beginning: “Pshhhh, Pshhhh, Pshhhh”. Make sure the sound is shrill and strident. Do it in a sequence of three, repeating the se­quence two or three times. At first, you’ll probably need to pish fairly loudly, but you can lower the volume once the birds get closer. Continue pishing for at least a couple of minutes after the first birds appear. This will give other species that may be present a chance to make their way towards you. Chickadees and nuthatches are especially receptive to the pishing sound, but other species like warblers, wrens, finches and sparrows will usually approach as well.

Quite often, the birds that are attracted by pishing are actually feeding together in loose flocks. For example, chickadees that glean insects from leaves, bark and punky wood are often found in the company of nuthatches, woodpeckers, kinglets and warblers that are searching for similar – but usually not identical – food items. Having more individuals searching for food increases the likelihood that a rich feeding patch will be located and food-poor areas can be avoided. Individuals probably also learn about new food sources from other species. In one study, titmice were observed visiting a site where a woodpecker was pecking at bark. It quickly began foraging in the same place. Mixed-flocks are most common outside of the breeding season.

Blackbirds

By mid‑July, most Red-winged blackbirds have finished breeding. Males lose their intolerance of one another and form feeding flocks, which roost together at night. Initially, these flocks are small and include only the adults and young of local breeding populations. However, as summer advances, these smaller roosts will begin to break up and much larger flocks form. A mixing of different species occurs, too, with common grackles and European starlings often joining in with the red-wings. The roosts are often cattail marshes, thick stands of alders or even upland woodlots.

A flock of Red-winged Blackbirds over a Kansas field – Bob Webster

 

 

 

 

 

 

 

 

Starlings and crows

For city dwellers, starlings and crows are usually the most noticeable roosting species during the summer months. Large deciduous shade trees are the preferred roosting sites. Thousands of starlings may occupy a given stand of trees and will sometimes return each night until the leaves drop. As sunset approaches, the birds start arriving in the vicinity of the roost and perch in nearby trees, often making frequent, noisy flights from one tree to another. This activity, known as staging, goes on for about half an hour before they actually settle into the roost trees. For nearby residents, the noise and commotion can be irritating to say the least.

Watching a flock of starlings take flight and then change directions simultaneously is fascinating. How does the group manage to turn and maneuver, almost as a single unit? As it turns out, the behaviour does not depend on the actions of any one “leader” but is rather a property of the group itself. The maneuvering of the flock, known as a murmuration, is determined by the second‑to‑second decisions of individual birds as they respond to what seven – yes, exactly seven – of their flock neighbours are doing. When one bird changes speed or direction, its seven closest neighbours do the same. In this way, the information spreads almost instantaneously across the flock. Google “flight of the starlings” to see a beautiful video of a murmuration filmed in the Netherlands.

A murmuration of European starlings over Minsmere in the United Kingdom – photo by Airwolfhound

 

 

 

 

 

 

 

 

Crows, too, often congregate in the hundreds or even thousands to sleep in communal roosts. An hour or two before darkness, they start flying to peripheral congregation sites, located close to the overnight roosting spot. There is usually a lot of noise-making, chasing, and general squabbling that goes on at these sites. Then, right at dark, the crows move on to their nearby final destination.

What to watch for this week

Young frogs are transforming into adults and leaving their natal ponds. Watch for tiny (less than one centimetre in length) wood frogs, spring peepers and American toads on moist areas of the forest floor from July through September. In backyards and parks, listen for the buzzy, electric song of the first dog-day cicadas of the summer.

 

 

Nov 022017
 

Much remains to be explained about these familiar birds    

When a species is as common as the blue jay, we tend to take it for granted. We are often dulled into thinking that there’s little new to be discovered about its behaviour. Well, think again. From their aggressive mobbing behaviour and seed caching, to their enigmatic migrations and mimicking of other species, there is much that remains a mystery. We even have to be wary of our own senses. A jay’s feathers, for instance, aren’t really blue. The colour pigment they contain is actually brown. The blue we see is caused by the scattering of light by special cells in the feather barbs. The feathers appear almost black when backlit.

Food

A big part of the blue jay’s success as a species comes down to being a generalist. They will eat everything from seeds and nuts to insects and carrion. Even the eggs and nestlings of other species are sometimes on the menu. When jays visit feeders, they prefer peanuts, suet and sunflowers offered up on a tray or hopper feeder. Just this week, I watched as one jay gobbled up at lest 20 sunflower seeds, before flying off presumably to cache them.

Jays have a pouch in the throat and upper esophagus in which they transport food – as many as three acorns at a time, for example. They then store the food in caches – often in the ground – to be eaten at a later date when the pickings are scarce. One study showed that a single blue jay can cache up to 5,000 acorns over the course of an autumn. Some of the food, of course, is never eaten, so acorns can end up germinating and producing new trees. It is believed that jays are responsible for the spreading of oaks after the glaciers retreated. However, the extent of caching appears to differ widely among individual jays.

Because this year’s crop of acorns, beechnuts, hickory nuts and beaked hazelnuts is quite good, it appears that large numbers of jays will remain in Kawarthas this fall and winter. I am already seeing a lot more than this time last year. But, as we’ll see later, the link between food availability and migration is far from clear. Although much of their winter diet consists of acorns – at least in parts of their range – jays cannot survive on these nuts alone. Some of the literature even states that jays don’t really care for the acorns of red and white oaks, which are the two main species here in the Kawarthas. Go figure.

It was once thought that the eggs and nestlings of other species made up a big part of their diet, too. This habit even attracted the attention of John James Audubon, who wrote, “It robs every nest it can find, sucks the eggs like a crow, or tears to pieces and devours the young birds.” The actual extent of nest predation, however, is unclear. Recent studies show that eggs and nestlings make up a negligible part of a jay’s diet.

In one famous study on the palatability of monarch butterflies,  captive blue jays were fed monarchs. As caterpillars, the monarchs had been raised on milkweed leaves, which is the only plant the larvae will eat. Ingesting the butterflies caused the jays to vomit, and they refused to ever dine on them again. It is now a well-known fact that monarchs are unpalatable to birds.

Migration

We have blue jays in the Kawarthas every fall and winter, but the number varies significantly from one year to the next. Fall migration is most noticeable in mid- to late September, although it does continue until the end of October. Jays return to the Kawarthas in May, when migrants arrive back to join their brethren who never left.

The best place to observe fall migration is along shorelines of Lake Ontario and Lake Erie, where thousands can be seen daily. The birds fly in a loose, string-like flocks ranging in size from about six to over a hundred jays. They travel during the day- especially in the morning – and are usually silent. In the autumn of 2007, hawk watchers at Holiday Beach, south of Windsor, counted 50,000 jays streaming past in a single day. That being said, it is believed that no more than 20 percent of the population migrates, even in northern parts of the blue jay’s range.

No one has figured out why an individual jay or jay family migrates when or if they do. Some individuals migrate south one year, stay north in their nesting area the following winter, and then migrate again when the next fall rolls around. Individuals that depart an area in autumn may be replaced by those migrating from farther north. It was once thought that young jays migrate more than adults, but recent analyses of banded jays show no significant age difference between migrant and resident birds. Migration may indeed be related to the availability of wild food, but this is not yet certain.

Vocalizations

“Along the line of smoky hills / The crimson forest stands / And all the day the blue jay calls / Throughout the autumn lands.” These words by the Canadian poet William Wilfred Campbell are as true today as they were in 1889. The loud and brash calls of jays are maybe the most typical bird sound of early fall. Blue jays are well known for their large variety of vocalizations, the most familiar of which is a shrill, descending “jaaay” scream. They also make a whistled “toolili” sound, which is often referred to as the “rusty pump” call, since it resembles the sound a hand-operated water pump. Quiet, clicking rattles are also common. Unlike other songbirds, blue jays don’t sing as such. This may be because they are not territorial and don’t appear to defend a discrete space the way that robins do, for instance.

Jays are also mimics and do an amazing rendition of red-shouldered hawk calls. Why they do so is unclear. It may signal to other jays that a hawk is present, or it may be a feeding strategy. Upon hearing the jay’s uncanny hawk imitation, some birds immediately fly away. The jay then eats the food left behind or raids its nest. Like migration, this is an area where much more research is needed.

Jays also use body language to communicate. Holding the crest down low, for example, indicates a lower aggression level. The opposite is also true. Watch the next time you see a blue jay squawking: the crest is usually erect.

Mobbing

Jays, like crows, blackbirds and chickadees, often take part in mobbing behaviour, which refers to a group of birds fluttering and calling loudly around a perched hawk, owl, cat or other predator. The purpose of this behaviour is still debated, but it seems to be done in an effort to hound the intruder until it decides to move along. In the case of a hawk, it is not clear why the pestered raptor doesn’t simply turn on its tormentors and grab one or two for an easy meal.

Abundance

Blue jay populations have remained constant for years, despite some mortality in recent decades from West Nile Virus. The 2000-2005 Ontario Breeding Bird Atlas shows a small northward extension of range, possibility because of more people feeding birds. Jays are most abundant in the southern shield region, which includes The Land Between. You can also find large numbers of jays in older urban and suburban areas of large cities throughout southern Ontario. Like many generalist species, jays adapt easily to changes in the landscape, and their populations may actually increase with climate change.

Male vs. female

People have often wondered how birds like blue jays and Canada geese recognize the opposite sex. In both species, the male and female appear identical to human eyes. The only apparent difference between individual jays – but not the sexes – is the size and shape of the black bridle or necklace across the nape, face and throat. This may help jays recognize different individuals.

Research now is revealing that birds have much better colour discrimination than humans. They see an entire range of colours that we cannot perceive or even imagine. This includes colour in the ultraviolet range. This means that birds may actually be seeing distinct differences in plumage colour. They may see colours that are unimaginable to us such as a blend of ultraviolet and yellow. Colour, of course, is a construct of the brain.

In one study, a stuffed male and female yellow-breasted chat, a type of warbler, were placed in a cage with a wild, living male chat. Since it was the breeding season, the wild male attacked the stuffed male in an effort to chase it from the cage. However, it displayed mating behaviour in front of the female. There is an important lesson here. As humans, we must learn to be much more modest about how we perceive the world. We have evolved in a limited perception bubble. We have significant sensory shortcomings and are by no means the pinnacle of evolution. In evolution, course, there is no pinnacle – just differences. As Joe Smith wrote recently in Cool, Green Science, “We must accept that as beautiful as birds appear to us, we will never be able to behold their true colors. We are left only to revel in the known unknowns and wonder about the ‘unknown unknowns’ yet to be discovered in the invisible world around us.”

 

 

 

 

 

 

Jan 132017
 

Here is a picture of an American Crow sending out the alarm, regarding this Red-tailed Hawk in our poplar tree. There were two other crows not in the photo also circling around the hawk and creating quite a ruckus. Shortly after this photo was taken, the four birds flew off.

Helen and Larry Keller, Mark St., Peterborough

Crow harassing Red-tailed Hawk – Helen & Larry Keller