Vancouver Avian Research Centre

.....Research - Conservation - Education

Summer (June/July) 2017

Setting 3.45 am alarms to get to the banding station pre-dawn is tough during the summer months especially when it's the weekend and everyone else is having a lie-in but it's totally worth it when the mist rises over the old-field habitat where we band and nets are opened for another banding session!

Bird of the month had to be this unique and quite spectacular after hatch year male hybrid Anna's / Rufous Hummingbird!

Hummingbirds and ducks are the families of birds that are known to hybridize a lot of course but usually within the same genera such as Anna's and Costa's Hummingbirds in California for example. But a hybrid cross genera like this Anna's (Calypte) and Rufous (Selasphorus) is much rarer.

The following photographs show the phenotypic traits that were suggestive of each parent.

The two head shots above of the hybrid show phenotypic traits of both species as can be seen by comparing both adult male Anna's and Rufous Hummingbirds below.

The combination of these traits was a perfect blend of the two species with green on the back (like Anna’s) with some rufous on the sides (like Rufous) and gray below (like Anna’s) and iridescent pinkish-red feathers covering the throat, chin and forehead (somewhere between Rufous and Anna’s!)

Adult male Anna’s (below left) has green on the back and flanks and gray below with no rufous on the body and iridescent magenta-pink feathers covering the entire head and throat.

Adult male Rufous (below right) has rufous face, sides and nape and a mostly rufous back  and an iridescent red throat and chin not extending on to the head.

The rectrices of the hybrid also showed phenotypic traits of both species, the central rectrices similar in shape and colour to an adult FEMALE Rufous and the outer rectrices similar in shape to female Rufous but in colour to male Rufous!

Anna’s rectrices are broad, green and with black (adult males) or white tips (females and immature males).

Rufous rectrices are primarily rufous with black tips (adult males), the central rects narrow and pointed, the central rectrices of females are broader and green with some rufous at the base. (photos below)

A SECOND Anna's / Rufous Hummingbird hybrid was captured at the end of July, this time a hatch year (HY) male showing the same phenotypic traits of both species and almost certainly an offspring of the adult male above!

It’s perhaps likely that hybrids in suburban-residential areas will become more common as these massively disturbed habitats allow for species that are not normally found in the same localities like Anna's (resident) and Costa's (summer visitor) in California which is similar to Anna’s and Rufous here but our two are in different genera which makes this all the more exciting and it will be interesting to see if these birds overwinter here like Anna's or attempt to migrate like Rufous!

Thanks to BICs Debbie Wheeler and Kerry Kenwood for taking charge of the June Bird Monitoring and Banding Workshop when another full house spent a long weekend learning about molt and ageing of North American landbirds in the hand.

We also welcomed Dutch Ringers Klaas and Annemieke van den Berg to the station. Klaas and Annemieke were on a month's trip to western Canada and had to include a visit to Colony Farm! Klaas got to see a whole bunch of target species and Annemieke got her wish to see Hummingbirds in the hand. In return we asked them to send us a Bluethroat when they got back!

It's was great to meet you guys and hope to see you again in the future!

And also Polish ornithologists Leszek and Małgorzata Bujoczek who for some reason missed the photo op! But it was great to see you guys too and safe travels on to the Rockies and on your way home!
The North Vancouver Ecology Centre NatureKids came by for their annual visit to the banding station. We've talked previously about the importance of our outreach and education programs to raise awareness of environmental issues as they relate to birds and this letter from this little girls parents sums up how impactful these sessions can be for children.
June and July is the nesting season for many songbirds when a lot of energy is invested in to young, building nests, incubating, attending dependant nestlings and for some species repeating this exercise up to 3 times a season!

It's not surprising that some songbirds like crows get territorial and defend their young when this much energy has been expended in to raising them!

We found two Black-headed Grosbeak nests close to the banding station. Black-headed Grosbeaks build very loosely constructed nests often making it easy to see eggs through the bottom maybe to provide ventilation to keep  eggs and nestlings cool. They are typically placed in the outer branches of a small deciduous tree or bush and often not well concealed leaving them vulnerable to predation. Such was the situation with the two nests we found, one of which failed completely after eggs were taken and the other which managed to successfully fledge just one nestling!

Breeding birds develop breeding characteristics which help us to separate males from females in sexually monomorphic species which otherwise look exactly alike.

Many species are sexually dimorphic meaning we can sex the bird based on characteristics such as plumage coloration and/or size. But in sexually monomorphic species both males and females look identical and these species can only be sexed in the hand in spring and summer when they show these breeding characteristics i.e. a cloacal protuberance (CP) or a brood patch (BP).

In many monomorphic species, the male's cloaca becomes enlarged and bulbous during the breeding season, the base narrow and tip swollen, the purpose being to store sperm and aid with copulation. This is called a cloacal protuberance and is illustrated in the photo below left of a male Song Sparrow with a fully developed CP.

Female passerines on the other hand conduct most if not all of the incubation and develop brood patches (BP). At this time they will lose the feathers on the breast and belly to facilitate direct skin contact and maximum heat transfer to the eggs for incubation.

The photo below right shows a fully developed brood patch with wrinkled and vascularized skin. The development of the brood patch progresses in stages similar to the development of the cloacal protuberance of the male, the feathers of the breast and belly are first shed and the blood vessels under the skin increase in size and number until the brood patch is edematous (i.e. vascularized and swollen) such as in the photo below right of a female Black-capped Chickadee with a fully developed BP.

The result of all of this breeding activity is, of course, baby birds which undertake the prejuvenal molt in the nest prior to fledging and which produces the bird’s first set of non-downy feathers called juvenal plumage.

Many of these very recently fledged young birds are incapable of sustained flight because their wings and tails are not fully grown, and are dependant upon parents for food. As we have said before, we always flag these birds by attaching red pegs to the bird bags they are in which alerts the banders to give them first priority for rapid processing at the banding station and then to take them back as soon as possible to a location near where they were captured.

Baby birds like this hatch year Swainson's Thrush show all of the characteristics of juvenal plumage.

The first is dull, streaked or spotted plumage. Recently fledged birds normally spend the first part of their lives either on or near the ground where they are vulnerable to predation. Dull, streaked or spotted plumage acts as camouflage to help protect them during this time. The buffy teardrops along the rachis of the lesser and median coverts shown here are diagnostic of juvenal feathers of members of the Catharus thrush family and are often present on retained juvenal greater coverts following the preformative molt after the breeding season.

These "baby" birds also have soft, fleshy, pinkish or yellowish gapes as shown here although some species, particularly some finches and thrushes can retain fleshy gapes even as adults.

Other characteristics of birds in full juvenal plumage include very loosely textured feathers, particularly the undertail coverts as shown below of the hatch year Swainson's Thrush above.

Around the base of shaft they are more downy and toward the tip show a reduced area in which the barbs are linked by hamulus-barbicel hooks to form an interlocking vane, the barbs spaced more widely apart along the shaft giving the juvenal vane a coarser look.

The feathers of the underwing (photo below left) and tibiotarsus (photo below right) develop later and are often devoid of feathers as shown below in the photos of the same bird.
Yet another characteristic of birds in juvenal plumage is very dull, brownish eye colour as shown in this hatch year Spotted Towhee.

Some more baby photos from top left clockwise, Song Sparrow, Common Yellowthroat, House Finch and Spotted Towhee. Most hatch year birds in full juvenal plumage cannot be reliably sexed but some like the Spotted Towhee can as males like this one have blackish rather than brownish flight feathers.

Juvenile European Starlings can be sexed based on the colour of the iris which is dark brown in males and pale grayish with a yellowish tinge in females.

Although there are an estimated 200 million or more European Starlings in North America they are uncommon birds for us at Colony Farm normally only seen in over flight above the old fields where we band so the occasional one that turns up in a net is always blog worthy like this one!

We continued with our Tree Swallow special species study involving radio frequency identification (RFID) technology. RFID allows the unique identification of individuals and automated recording of the presence of tagged birds at fixed locations such as nest boxes.

The technology is being used to better understand the connections between adult nesting behaviour, weather, food availability and nestling growth and survival.

For details of this project please see the photo essay in the spring/summer 2015 blog.

All this talk of research and science can't take away from the total cuteness of these baby birds which we all fall in love with and it's easy to see why!

It was also an opportunity to try out our new cuteness scale which seemed to be working pretty well! (photos below: Tree Swallow, Cedar Waxwing and Golden-crowned Kinglet)

Next up was a juvenal Gray-headed Cowbird - OK not a Gray-headed Cowbird but a juvenile male Brown-headed Cowbird with an unusually gray head!

Like crows, cowbirds get a very poor rap being blamed for songbird declines but the fault lies squarely at the door of humans for the continuing conversion of forest to agriculture and other land uses.

Originally birds of the open grasslands following cattle herds in search of seeds and disturbed insects Cowbirds evolved to become brood parasites, laying their eggs in the nests of other birds and abandoning their young to foster parents as they continued their nomadic lifestyles.

In the course of a single nesting season, a female cowbird may produce as many as 40 eggs over as many or more days. The challenge for her is she has to find as many nests of potential host species at just the right stage of laying in order for just a few of her offspring like this one to have the chance to survive to independence. This is actually about the same number of young that many cowbird host species themselves will raise in a single season by tending just one or two nests containing four or five eggs each!

The challenge is when cowbird nesting success almost completely eclipses the nesting success of its host species particularly in small forest fragments surrounded by agricultural landscapes. Some of these fragments are large enough to attract forest nesting host species such as Thrushes and in these areas the hosts experience exceptionally heavy cowbird parasitism pressure
due to the fact that a very large population of cowbirds is supported by the ever expanding surrounding agricultural landscape. This can cause what is known as a "population sink" meaning the host species may effectively raise only cowbird young but again, the irrefutable negative impact of cowbirds on some host species in such areas is symptomatic of the continuing conversion of forest by human beings!

Swallows are part of the guild of aerial insectivores which have suffered precipitous declines in recent years with research in Canada showing that populations of Barn and Bank Swallows to have fallen by 70% and Cliff, Northern Rough-winged Swallows and Purple Martin by over 50% in the past two decades.

The old field habitat at Colony Farm is critically important to these aerial insectivores and 7 of the 8 species of NA swallow are found there sometimes in large numbers.

Northern Rough-winged Swallow is one of the less common swallow species found in the Park nesting in burrows and cavities in various substrates including pipes and other man made structures.

It gets its name from the serrations on the leading edge of the primary feathers which are distinctly hooked in males and smaller and straighter in females. The edge really is rough to the touch and similar to running a finger along the edge of a coarse file!

The photo below show the leading edge of the outer primary at 5 times magnification (photo. credit Dev Manky). The function of the rough wing edge still isn't known.

By the end of July many birds have already started their prebasic molt like this after hatch year (AHY) male American Robin at the very beginning of its definitive prebasic molt which includes all body and flight feathers normally starting with the lesser and median coverts, then tertials and innermost primaries and corresponding primary coverts although this bird had yet to molt its tertials.

And a nice story to end the blog when neighbours found a baby Barred Owl on a trail at the back of our house when they were out walking their dog on May 8th. At the time it was just a bundle of fluff that appeared to have fallen out of a nest cavity high up in tree. We were away in Toronto so they called the folks at Orphaned Wildlife (O.W.L.) where we band all the rehabbed raptors. It was taken in and fostered by their resident pair of Barred Owls and brought back for release.

After a few photos we released it and it flew to the eaves of the house, sat there for a while getting its bearings and then flew off in to the forest!

The photos show what a difference a couple of months make in the life of a young owl!

As always a massive thank you to all of VARC's dedicated volunteers without whom none of the work we do would be possible. It never ceases to amaze me when we turn up at the park gate at 4.45 am to see everyone gathered - definitely a few sleepy faces and yawns but everyone happy and excited for another banding session! What a truly great group of people! Thanks again!

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