the Nest Files – Prairie Warbler

Adult male Prairie Warbler (D.Derbyshire)


Prairie Warbler (Dendroica discolor)

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!

the Nest Files – Herring Gull

Adult Herring Gull (Derbyshire)


Herring Gull (Larus argentatus)

Nidiologicals – Peck and James (1987) and R.J. Pierotti and T.P. Good (1994)
Habitat – Primarily Islands, rock islets, coastal areas and open mainland sites.
Microhabitat – Nest scrape/mound often sheltered from wind by rock, log or vegetation. Usually on ground but sometimes elevated in vegetation or man-made structures.
Spring arrival – Most breeding adults are non-migratory but return to nest sites in March-April
Nest builder – Male and female
Average # of broods/season – 1
Average egg laying date – 26 May-9 June (Ontario)
Average clutch size
– 3 eggs
Incubation period – Average 30 days
Egg description – Large, ovoid with variable base colour ranging from light olive, brownish to greenish with brown to black markings.
Incubation – Male and female

Herring Gull nest with eggs (Derbyshire)

The circumboreal Herring Gull is one of two common breeding gull species in Ontario. The Herring is more numerous from central Ontario north to Hudson Bay while its close relative the Ring-billed Gull is more abundant in the south. By the late 19th century the Herring Gull was nearly driven to extirpation from North America by plumage and egg collectors but their numbers have recovered and have possibly even exceeded precolonial abundance levels (Pierotti 1994). In Southern Ontario they tend to occur in large colonies with Ring-billed Gulls along the coasts of large lakes. However, this species is more widespread in the Southern Shield region where thousands of inland lakes dotted with rocky islands provide abundant breeding habitat. Smaller colonies or isolated nestings are more typical in the Southern Shield, although the species abundance and ecology appears to be less well known in this region.

Herring Gull nest site (Derbyshire)

A waterbird breeding colony consisting of Ring-billed Gull (10-12 pairs), Great Blue Heron (2 pairs) and Herring Gull (1 pair) was found on a small island on Big Clear Lake in early June of this year. A followup visit revealed at least 10 active nests of Ring-billed Gull, 2 of which contained young. The Ring-billed nests were fairly tightly spaced along the western slope of the island where low ground vegetation was densest. The Herring Gull nest was isolated from all other nests at the northern edge of the islet abutting some large rocks (note inserted white circle in above photo). The eggs were just beginning to hatch on June 11, 2010.


This photo, with FBS assistant Seabrooke standing in the background, provides some sense of scale of the large nest mound constructed of mostly pine needles, moss and lichen. Herring Gulls have a reputation as fierce nest defenders, even toward human territory invaders. This particular pair were quite docile and accepting of our intrusion, although we only visited the nest very briefly to snap a few photos and check the contents of the nest. Here you can see the nest tucked up against some rocks, which would have provided protection from the cold north and west winds blowing down the lake.

'Gull' rock on Big Clear (Seabrooke Leckie)

Lastly, here is the rocky islet itself. The islet is little more than 800 square metres in size but it has the sought after expanses of barren rock with low vegetation – ideal for nesting gulls in the Southern Shield. The islet is also attractive to nesting Great Blue Herons. Two active heron nests were found in the crowns of Eastern White Pines and the young are still being fed as of July 2, 2010.

the Nest Files – Chestnut-sided Warbler

Adult male Chestnut-sided Warbler (Derbyshire)


Chestnut-sided Warbler (Dendroica pensylvanica)

Nidiologicals – Peck and James (1987) and Richardson & Brauning (1995)
Habitat – Early successional deciduous forest, regenerating clearcuts/fields and woodland edges
Microhabitat – Open cup nest built in crotch of understorey shrub, usually less than 2m from ground.
Spring arrival – Early to late May (Ontario)
Average nest height – .6m
Nest builder – Female only
Average # of broods/season – 1
Average egg laying date – 7 June-17 June (Ontario)
Average clutch size – 4 eggs
Incubation period – Average 11-12 days
Egg colour – White to pale greenish with variable markings concentrated at larger end.
Incubation – Female only
Brown-headed Cowbird host – Yes

CSWA nest with eggs

The Chestnut-sided Warbler (CSWA) is a fairly common breeder here in Frontenac County and across much of the southern half of Ontario. This species was a North American rarity in the early 19th century before much of the forests were cleared and the young successional habitats became widespread. Populations of Chestnut-sides exploded and now occupy scrubby margins of woodland and overgrown fields from central Saskatchewan to Nova Scotia and south to Georgia along the Appalachian Mountains. In our region they are typically associated with woodland borders of small farms, roadsides, bogs and rock barrens.

This nest was discovered by the observation and tracking of a female carrying nest material on May 28, 2010 at our Blue Lakes MAPS station near Sharbot lake, ON. There are about ten pairs in the immediate area of the station that are occupying scrubby shoreline edges of lakes and ponds. At least part of the site was burned over at some point within the last century or so, which has slowed regeneration and created appropriate conditions for the species. The nest pictured above was less than half complete on May 28 and was finished by June 4 when three eggs were photographed.

Full clutch (Seabrooke Leckie)

A clutch of five eggs is unusual for this species. This picture was taken on June 8 during our first visit to Blue Lakes. We captured and banded two males and the female responsible for this clutch on that date. The males have an interesting song repertoire and vocal development biology. Two song classes are evident; an Accented Ending (AE) class and an Unaccented Ending (UE) class. The AE song (Please, please, pleased to meetcha) is given on arrival and is primarily used to attract females. The UE song is given later on in the breeding season and seems to be mostly employed for territorial defense and intraspecific aggression. Lab studies have indicated that AE songs are developed with little social interaction while UE songs are learned through direct observation of “tutor” males (Byers and Kroodsma 1992).

Chestnut-sided Warbler nest site

Here is a photograph of the nest site context along the shore of a small unnamed lake. The Chestnut-sided Warblers are nesting in this low, dense shrub layer beneath scattered clumps of young-mid successional oak and maple. Gray Catbird, Warbling Vireo, Yellow Warbler and Indigo Bunting also occupy this habitat type, although the latter is mysteriously absent from the site. We have about five more weeks of fieldwork in 2010 and a lot yet to learn about the “Chestnuts” at Blue Lakes. We are suspecting that the forthcoming post-breeding dispersal will consist of a large dose of young Chestnut-sided Warblers.

Young CSWA at MABO in 2009 (S.Leckie)


the Nest Files – Yellow-billed Cuckoo

Yellow-billed Cuckoo nest with eggs


Yellow-billed Cuckoo (Coccyzus americanus)


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


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.



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

the Nest Files – Louisiana Waterthrush

Female LOWA entering nest


Louisiana Waterthrush (Seiurus moticilla)

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

– 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


Nest building in progress


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.


Nest complete with eggs


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.


Nest contents


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.



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.


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.