Adult male Prairie Warbler (D.Derbyshire)

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Prairie Warbler (Dendroica discolor)

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Nidiologicals – Peck and James (1987) and Nolan,V.,Jr., E.D.Ketterson, and C.A.Buerkle (1999)

Habitat – Dry, early successional shrubland habitats ranging from pine plantations, dunes, mangroves, barrens, clearcuts and abandoned fields.
Microhabitat – Cup nest usually well concealed in upper crotches of shrub
Spring arrival – Early to mid May (Ontario)
Average nest height – .6m-.9m
Nest builder – Female only
Average # of broods/season – 1-2 (variable with latitude and local conditions)
Average egg laying date – 8 June-19 June (Ontario)
Average clutch size – 3-5 eggs
Incubation period – Average 12 days
Egg colour – White to greenish white with variable brown spots, usually wreathed at larger end.
Incubation – Female only
Brown-headed Cowbird host – Yes

Prairie Warbler habitat (nest site in foreground)

The Prairie Warbler is a rare but regular breeding species in Ontario. It is estimated that about 300 pairs occur annually in the province, although there is some evidence of recent decline due to habitat succession of granitic rock barrens along the edge of the southern shield region. We’ve been surveying and studying Prairies in Frontenac Provincial Park for the last two years and have found a small but apparently healthy population in open barrens with scattered young trees and pockets of dense shrub cover. The above photo was taken within the core breeding area, which is about 20 hectares in size and characterized by low tree cover, exposed rock, dense ground vegetation and thick patches of vibernum sp. and junipers. Most Prairie Warbler territories here are associated with sloped shoreline edges of beaver ponds and lakes, which may be a function of denser shrub growth occurring in lower lying areas.

Shrubs along rocky slope (nest site in foreground)

This photo shows a typical nest site along a rocky slope where Downy Arrowwood (Viburnum rafinesqueanum) proliferates. Four nests have been found so far this summer and all but one were positioned near the top of a viburnum at heights between .7m-1.3m. All four nests have been located along slopes ranging from gentle to sharp and with no apparent preference for aspect.

Prairie Warbler Nest with eggs

Prairie Warbler nests resemble those of the Yellow Warbler (Dendroica petechia), a fairly close relative but less common inhabitant of the rock barrens. Prairie Warblers favour hot and dry environments while Yellow Warblers tend to occupy wetter shrubland habitats with a more flexible tolerance for shade/canopy closure. This nest with four eggs was discovered on June 26 when a female was flushed from a small clump of viburnum. When incubating female Prairie Warblers notoriously sit tight and only flush when very closely approached.

Nest in viburnum

This is a shot of the same nest within the shrub. Prior to nest searching this season I was anticipating that Ground Juniper (Juniperus communis) would be the most common host plant for nests but it seems that the viburnums are more abundant and probably preferred here. They are a stout and sturdy shrub with woody main stems and branches, while the leaf cover provides excellent concealment and weather shielding from all sides. The only non-viburnum nest was located in a lonicera sp. that grew within a large clump of Downy Arrowwood.

Prairie Warbler nest with five young (5-6 days old)

Two of the four nests were found by patiently following adults carrying beakfulls of plump, green caterpillars. One of our colour banded males (nickname “Whitey”) led me to this nest with five young. Thanks are due to Julie Zickefoose for helping Seabrooke and I age these nestlings. These little prairielets were identified as being 5-6 days old and only a few days away from leaving the nest.

Incubating female

This female was photographed incubating on June 26. When I returned five days later I was disappointed to find that the nest had failed, probably due to predation. Common Grackles, Blue Jays and snakes would be the most likely nest predators in the barrens. I’ve twice found Ribbon Snakes (Thamnophis sauritus) above the ground within shrubs here. On the upside it appeared that the female, or perhaps a different female, was preparing to rebuild within the territory or perhaps even reuse the failed nest. The attached male (also colour banded) was singing vigorously while the female inspected forks of shrubs and called softly. On two occasions she was observed for five-minute periods shaping and touching up the failed nest. Hopefully the second attempt will fair better than the first!

May 30th was probably one of my top 5 most enjoyable days of fieldwork since Frontenac Bird Studies began. The weather was perfect, the biting insects were oddly subdued and I could scarcely walk 100m before needing to georeference some exciting critter. I saw many butterflies, moths, snakes and plants of note but the centerpiece was a wetland that Steve Gillis and I explored during our first biothon in July 2010. Below are two panoramic views of the swamp from the south and east respectively (click to enlarge).

The wetland is fairly large by frontenac standards, about 9 acres in total area. It is distinctive in having a small raised island of live trees (mostly pine) surrounded by a flooded lowland dotted with snags and fallen trees. Surrounding the wetland is mid-successional oak-maple forest with scattered mature trees, an open understorey and with ground cover dominated by grass. The area was absolutely teeming with cavity nesters – Northern Flickers, Hairy Woodpeckers, Yellow-bellied Sapsuckers, Great Crested Flycatchers and White-breasted Nuthatches mostly. Apparently the area is so irresistible to Common Grackles that they were also nesting in cavities 10-15m above the water – an unusual choice for them (1.8% of nests reported to Ontario Nest Records Scheme n=2652).

At the far north end of the swamp were two large platform nesting species – Osprey (1 nest) and Great Blue Heron (3 nests). These and the all the cavity dwellers put on quite a show! The bordering woodland was also active with Cerulean Warblers, Red-shouldered Hawks, Yellow-throated Vireos and a single Olive-sided Flycatcher being the most noteworthy. The Olive-sided is the first I’ve seen in the region and probably a migrant, although suitable is available north of the park closer to highway 7. You can hear it singing in the video clip above (quick-three-beers) along with the odd Cerulean Warbler.

The birding at this site in July of last year was less memorable, probably due to the fact that it was during a mid-afternoon in July. However we did spot a pair of Red-headed Woodpeckers that day (Melanerpes erythrocephalus) – a rapidly declining species (Threatened status) in Ontario. It turns out that the species has been retracting from many parts of its range but heavily in Eastern Ontario. Our observation was the second of only two documented breeding records for Frontenac Provincial Park, although breeding evidence was not officially obtained in 2010. I bookmarked this as a target for 2011 and am pleased to report that it took me less than 30 minutes to confirm an active nest site this past Monday!

Adult Red-headed Woodpecker near cavity

RHWO Nest Site (near top of snag just underneath foliage)

Their active behaviour and brilliant high contrast of their plumage made them easy to track and observe within the open wetland. An adult called repeatedly from the west end of the swamp but rarely approached the nest (the male?). The other adult, presumed to be the female, made frequent trips to a cavity near the top of a 14m tall snag close to the southeast shoreline. The video at the beginning of this post highlights some of the activity at the nest site, which seemed to be exclusively short incubation sessions as no excavation or food carrying were noted. We will return to this site again in the next week or two to check on its progress.

The Red-headed Woodpecker is an extraordinary bird for many reasons. This post is already running long so I’ll have to return to this topic at a later date to highlight its unique ecology and relationship with human settlement. Below are two instructive breeding evidence maps from the Ontario Breeding Bird Atlas, which visualize the widespread decline of this species in Southern Ontario. For further intormation, The Birds of North America account (subscription needed) is essential reading for this species but the Cornell account hits some key points too.

1st Atlas (Source: Atlas of the Breeding Birds of Ontario)

2nd Atlas (Source: Atlas of the Breeding Birds of Ontario)

This video was recorded yesterday while revisiting the site where a Louisiana Waterthrush nest was found on May 26, 2010. The stream at this site is flowing with so much vigor that the two waterfalls severely limit the audibility of my playback system. Despite this I was able to locate a territorial male at the south end of the stream complex in a low valley sandwiched between two small ridges. I promptly ended playback as soon as the male responded and watched him for about ten minutes or so as he moved back and forth from the stream to higher perches. At one point he moved higher toward the canopy and was instantly chased off by a bill snapping small passerine, which turned out to be a female Cerulean Warbler (Dendroica cerulea). I followed the female for several minutes and hit an ornithological jackpot of sorts when she flew to a nest located on a horizontal branch of a large Sugar Maple (Acer saccharum), about 15m above the ground.

Cerulean Warblers build their nests high in the upper canopy of deciduous forests that have mature trees, little or no understorey and small gaps or breaks in canopy closure. These characteristics make their nests quite difficult to find and even harder to inspect and monitor! In this case I was able to get a decent view of the nest from either of the two ridges, which put me roughly 15 feet closer to the crown of the large trees growing in the valley. Even with this advantage I still had to zoom to 39x to get a low quality recording. Gotta thank the 749 mosquitoes for all the shakiness. I will definitely be returning to this site (with a tripod!) to monitor both of these important breeders in the next several weeks. Frontenac Provincial Park is one of the most significant protected areas for Canada’s population of Cerulean Warblers now listed as an Endangered species by COSEWIC.

Playback and Bullfrog at the falls

Back to the waterthrush surveys. Things have picked up a bit since my last post but it seems that 2011 will be marked as a down year for breeding Louisiana Waterthrushes in this region. I have not been successful at several reliable sites despite as many as four repeat visits. A review of historical records show some evidence of a downward trend occurring since the first half of the last decade. Despite an apparent population decrease coinciding with the initiation of our study in 2010 it is critical to monitor the sites through the good times and the bad times. Interestingly, the high number of unoccupied sites found this year has only buoyed my interest in the study going forward. Also, the 2011 season is not over yet as surveys at five more sites are yet to be completed and I do have four active sites to keep tabs on.

Ferns and Jack-in-the-Pulpit

Gorge near Birch Lake

Deer Fly season begins

Nesting site along the cliffs across the lake

In this post from early June of last year I wrote about three recently fledged Common Ravens that were found near Clearwater Lake. This is a small but deep oligotrophic lake that is probably best known for its population of Brook Trout. I regularly pass through this area at this time of year and usually notice the clamorous activity of ravens along the lake edge. The noise reminded me to check the cliff for active nests when I passed by last week. It didn’t take long to spot the nest immediately above some rock covered in white wash. The following photos show an adult brooding and three youngsters waiting for food. Unfortunately the photos were taken from a distance of about 100m, which made them pretty grainy but the idea of leaning over the cliff for a better closeup just didn’t appeal.  Common Ravens are regular breeders in the area however this particular record was the first for us since we began in 2009 – very cool!

Incubating adult

Three nestlings

Nest guarding Ovenbird near Sharbot Lake

"The Look"

Veery nest in an old mossy stump (Seabrooke Leckie)

Female incubating the "stump nest"

Great Blue Heron nestlings at Blue Lakes

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Cuckoo nestlings

The Yellow-billed Cuckoo nest that was first described in this post from a few days ago now has two scraggly nestlings. Despite the mid-morning heat, an adult was incubating them when I arrived. These nestlings are about 4-5 days old, which indicates that hatching began shortly after my last visit on May 30. Bendire’s description of the young from 1895:

“The young when first hatched are repulsive, black, and greasy-looking creatures, nearly naked, and the sprouting quills only add to their general ugliness”

These younglings may not be the most aesthetically pleasing bird babies that I’ve ever seen but I like ‘em. They made amusing hissing and spitting sounds, which seemed to fit their general appearance and the character of their parents. There were three eggs on May 30 so I’m not sure what became of the third. Amazingly, these nestlings will resemble full blown Yellow-billed Cuckoos in just a day or two, which means this will likely be the last check on this particular nest.

Close-up

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Gull colony

Surprisingly, neither Herring Gull (Larus argentatus) or Ring-billed Gull (Larus delawarensis) are listed as species having bred in Frontenac Provincial Park. This may be an unintended omission in my source material as suitable habitat exists on many of the larger perimeter and interior lakes. Both species were found tending nests this morning on a small rocky island with a few large eastern white pines. There were enough nesting pairs to label this a colony. I only had time for a quick paddle by this morning but will return soon to accurately census the colony. I must remember to bring some sort of decoy to avoid getting hit by marauding Herring Gulls. I’m not too keen on the idea of capsizing the canoe in a cold lake that is 73 metres deep!

Incubating Ring-billed Gulls

Juvenile Common Raven

The raven is a personal favourite of mine. Steeped in lore amongst cultures around the globe, they are perhaps the most intelligent of all bird species and their remarkable behaviours can be witnessed throughout the year. A group of recently fledged Common Ravens (Corvus corax) were discovered in a stand of pine on the west side of Clearwater Lake last week. There was no sign of a nest in the treetops but there was a steep cliff on the opposite side of the lake, which may have supported a nesting pair. The youngsters were quite entertaining to watch and they allowed my approach for some decent photos and a better view. In between bouts of raucous calls and chatter to its siblings, this one concentrated on deftly breaking off and strutting around with twigs.

Close-up

This one seemed the youngest of the three. Here you can clearly see the fleshy gape at the base of the bill, a characteristic of nestlings and their hyper extended maws. Also, this juvenile has the gray eye colour of a very young raven, which will turn chestnut brown as the bird ages.

Wood Thrush nest and guarding adult

Finally, an image of one of several Wood Thrush nests in progress this spring. I snapped this photo of the nest with the adult on security detail. For several minutes It perched motionless and just stared at me. It had a certain look in its eyes that seemed to say ‘can I help with you with something?’. I quietly left it to its important work.
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Yellow-billed Cuckoo nest with eggs

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Yellow-billed Cuckoo (Coccyzus americanus)

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Nidiologicals – Peck and James (1987) and Hughes, J.M. (1999)

Habitat – Open woodland habitats with clearings and dense shrub cover.
Microhabitat – Nest concealed by foliage on outer branch or main fork of tree or shrub.
Spring arrival - Early to late May (Ontario)
Average nest height – 1m-2m (Ontario)
Nest builder – Male and female
Average # of broods/season – 1 (multiple broods may occur when food sources abundant)
Average egg laying date – 9 June-4 July (Ontario)
Average clutch size – 2-3 eggs
Incubation period – Average 9-11 days
Egg colour – Unmarked pale bluish green.
Incubation – Male and female
Brown-headed Cowbird host – Yes

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Adult incubating

The cuckoo family (Cuculidae) is a diverse group of over sixty species that inhabit all continents of the globe except for Antarctica. The Yellow-billed Cuckoo, like its relatives, has an unusual and complex breeding system. Yellow-billeds are non-obligate brood parasites, meaning that they will tend to their own nests but also lay eggs in nests of other birds, especially when food sources are abundant. They will deposit eggs in other Yellow-billed Cuckoo nests (intraspecific parasitism) but also target Black-billed Cuckoo, Wood Thrush, Gray Catbird and American Robin (interspecific). These species lay eggs that are most similar in appearance to their own (unmarked blue to greenish), thus suggesting egg-mimicry is involved.

Male and female Yellow-billed Cuckoos build their nests within a few metres of the ground, usually in areas with a dense shrub layer. Nests are loosely constructed platforms composed of twigs and sparsely lined with dried leaves, plant tendrils and bark strips (Hughes 1999). The nest pictured above was discovered on May 25, 2010. The lining of this nest included fresh leaves while a sprig of Reindeer Lichen was added later. Both sexes incubate but the male brings new material to the nest when subbing in for the female. There is a vast list of fascinating factoids about Yellow-billed Cuckoo nests but I was particularly struck when I read that young are reared from egg to fledgling in just 17 days! This particular observation is astounding….

At age 6-7 d (26-29 g), feather sheaths burst open; nestling methodically preens off sheaths with bill; within 2 h nestling is fully feathered, but tail is still short (Hughes 1999).

This almost supernatural feather growth is colourfully described by Dr. A.H. Cordier in 1932 as follows:

The first picture was made at nine o’clock. . . . This shows the young by the unhatched egg; the horny, sheathed feathers were fully two inches long, making the bird look like a porcupine. About ten-thirty the sheaths began to burst, and with each split a fully formed feather was liberated. This process took place with such rapidity that it reminded me of the commotion in a corn popper or a rapidly blooming flower. All the while I was within three feet of the bird, and could see every new feather, as it blossomed, so to speak.

At three p.m., six hours after the first picture was taken, I made another photograph, showing this same bird in the full plumage of a Cuckoo, except the long tail.

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I will be back to this nest very soon to check on its progress and also to sneak a peek at the young, which were described by Bendire in 1895:

The young when first hatched are repulsive, black, and greasy-looking creatures, nearly naked, and the sprouting quills only add to their general ugliness

This is the first Yellow-billed Cuckoo nest for our project but probably not the last. Both Yellow-billed and Black-billed Cuckoos are regular breeders throughout the Frontenac region. While much of the region is heavily forested with mature deciduous woods that are normally avoided by cuckoos, clearings created by wetlands, rock outcrops and ridgetops are abundant. Here in the arch, it is plausible that the Yellow-billed Cuckoo is yet another species benefiting from the rugged southern shield topography, low-intensity agricultural practice, shallow till and historical fires.

Cuckoo nest site

Female LOWA entering nest

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Louisiana Waterthrush (Seiurus moticilla)

Nidiologicals – Peck and James (1987) and Douglas Robinson (1995)

Habitat – Gravel bottomed streams flowing through mature deciduous or mixed forest. Also nests in wooded swamp habitats on occasion.
Microhabitat – Nest built in cavities of stream banks, upturned tree roots or fallen logs.
Spring arrival - mid to late April (Ontario)
Average nest height – 0m (always nests on the ground)
Nest builder – male and female
Average # of broods/season – 1 (multiple broods not reported)
Average egg laying date – May 3 – June 12 (New York)
Average clutch size – 5 eggs
Incubation period – average 13 days
Egg colour – Whitish, spotted or blotched with ruddy brown, usually concentrated at large end
Incubation – female
Brown-headed Cowbird host – yes

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Nest building in progress

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Another FBS first – a Lousiana Waterthrush nest! A territorial pair was first located on May 10th at this site but no further breeding evidence was obtained at that time. A followup visit on May 20th revealed both the male and female building this nest in the stream bank above a waterfall. So why the delay? It’s possible that an earlier nest was abandoned but it is more likely that nest construction was delayed after the pair bonded, which is typical according to previous studies (Robinson 1990). On May 20th the pair were observed entering the nest site, which at that time was bascially a mud bowl with a bulky leaf exterior.  The pathway of leaves visible here is a common feature of a Louisiana Waterthrush nest but is not always built. The above photo illustrates this ‘pathway’ constructed of dead leaves, which are noticeably damp and likely collected from the water. The wet leaves and the addition of mud are probably used for adhesion and support of the nest exterior and pathway.

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Nest complete with eggs

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There were four eggs in the nest this morning, which suggests that egg laying began by May 22nd at the latest (1 egg is deposited per day). There might be one more egg still to come as the average clutch size is five (Bent 1953). I watched the female incubate for about an hour before she slipped away for a break. The male was present, he sang on two occasions nearby and made short excursions to the waterfall but never approached the nest. With the female on break, I approached the nest to check its contents and snap a few quick photos.

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Nest contents

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The interior of the nest had transformed since my last visit. What was formerly an excavated mud bowl had become a neatly constructed cup nest lined with fine grasses, rootlets and animal hair.

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This last photo shows the nest site context. This would be considered a fairly exposed nest site for the species. This spot wasn’t on my radar during my initial scan of the banks along the waterfall. There were several other sites that would have been more enclosed, shaded and difficult for non-avians to access. You can just barely see the stream bottom in the lower left corner. Luckily, relocating this nest has always been instantaneous thanks to the convenient tree root pointing to its location! Waterthrushes never fly directly to their nests, instead, they approach the nest by walking from a distance as great as 10m – very typical behaviour for ground nesters. This is nicely demonstrated by the following video of the female at the nest from this morning – whom I could have watched for hours if not for the oppressive heat today. If all goes well, the eggs will hatch in 8-10 days and I’ll be back to check on the family in early June.

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Finally, here is a short video of an adult female LOWA at the nest from today’s visit. Just to avoid any confusion, I should mention that during the video you might hear a Northern Waterthrush singing nearby. The two waterthrush species “get along” very well and exhibit little or no interspecific aggression (Craig 1984). The video can be viewed at higher resolution here.
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