the Nest Files – Red-winged Blackbird

adult male Red-winged Blackbird (Derbyshire)


Red-winged Blackbird (Agelaius phoeniceus)

Nidiologicals – Peck and James (1987) and Yasukawa and Searcy (1995)

Habitat – Highly variable. Marshes, wetlands, fields, pastures and open woodlands.
Microhabitat – Nest usually woven into vertical shoots of a wide variety of substrates; commonly built within 1m of ground.
Spring arrival – March (Ontario)
Average nest height – .1m to 1.4m
Nest builder – female
Average # of broods/season – 1.7
Average egg laying date – 26 May-13 June (Ontario)
Average clutch size – 4 eggs
Incubation period – average 12.6 days
Egg colour – light blue-green or gray, marked with streaks, blotches and specks of black or brown. Markings are water soluble and fade during incubation (Nero 1984).
Incubation – female
Fledgling stage – young leave nest 10-12 days after hatching.
Parasitized by cowbirds – yes


Red-winged Blackbird nest contents


The Red-winged Blackbird is one of the most abundant and frequently studied bird species in North America. They are temperate migrants, returning to Ontario in early spring when males establish or reestablish territories in a wide variety of open habitats in upland and lowland environments. Red-wings breed across a vast range from boreal Alaska to Costa Rica. This range encompasses a considerable diversity of climatic and ecological conditions, which has certainly contributed to the total of twenty-six subspecies having been identified. Even more compelling is their complex social system. Up to fifteen females have been found to nest in the territory of a single male – making them one of the most highly polygynous of all bird species!


The nest pictured above was discovered in a medium sized palustrine marsh on Big Salmon Lake. The marsh was dominated by flooded grass and shrub growth as well as lesser quantities of cattail. Large numbers of Red-winged Blackbirds were present along with Swamp Sparrows, Yellow Warblers and Common Yellowthroats to name a few. The nest was located by accidentally flushing an incubating female. Given their abundant colonial populations, preference for open habitats and non-cryptic nature, it is not surprising that nests of this species are so frequently reported to nest record schemes. I was excited to find this one – a first for FBS. Red-winged Blackbirds can be found regularly in Frontenac Provincial Park but they occur in relatively small, isolated pockets where cattail and shrub cover is suitable.


Nest site


This last photo paints a picture of the nest site context (note the circled tuft of grass/shrub). The male held court over this section of the wetland while other occupied territories were being defended nearby. We don’t have waterbirds or wetlands as priorities for our studies at the moment but I expect we will turn our attention to these important areas in the future. Currently we are focused on species & habitats of conservation concern but we are fundamentally interested in keeping common birds common, such as the iconic spring harbinger – the Red-winged Blackbird.

the Nest Files – Field Sparrow

Adult Field Sparrow (D.Derbyshire)

Field Sparrow (Spizella pusilla)

Nidiologicals-Peck and James (1987) and M.Carey (1994)

Habitat=field, pastures and second growth forest edges and clearings
Microhabitat=nest built on or near ground; elevated in shrubs and tress later in breeding season.
Spring arrival=April
Average nest height=.2 to .5m
Nest builder=female
Nest building period=5-8 days in early part of season: 2-3 days in later part
Average # of broods/season= multiple (average of 2.9 in PA study).
Average Egg Date=26 May-21 June
Average clutch size=3-5
Incubation period=average 11-12 days
Egg colour=white or cream colour, heavily spotted on entire surface with denser markings at larger end
Fledgling stage=young leave nest 7-8 days after hatching
Parasitized by cowbirds=yes

Field Sparrow nest contents

The Field Sparrow, a close relative of the Chipping Sparrow (Spizella passerina), remains a common inhabitant of fields and various forms of scrub habitat in the eastern half of the United States, southern Ontario and Quebec. Rare north of the Southern Shield, the Field Sparrow has withdrawn from many areas in southern Ontario due to intensification of agricultural practices as well as the spread and maturation of forest cover in recent decades. They require open areas of dense low ground cover with some woody vegetation for nest support and song perches. It is likely that this species’ population reached its zenith in the 19th century when a low percentage of forest cover and low-intensity agriculture provided great expanses of suitable habitat. Here on the Frontenac Arch, the species remains abundant in rock barren habitats with its shallow till as well as abandoned farms. Forest fires would provide appropriate conditions for this species if not for current forest fire suppression practices.

The nest pictured above was discovered on a recent trip to one of our MAPS sites on crown land in the northern section of the FBS study area. Apart from farm fields, Field Sparrows are ubiquitously found in rock outcrops and in areas burned over in the mid-20th century. Eastern Towhee also occupy these areas and the two are almost always heard singing close together. This nest was actually the second Field Sparrow located at the site, the first of which failed for unknown reasons in early June. In both cases the nest was found elevated in a shrub, although this more recent example is considerably higher than the first, a typical response of the species to the increased growth of vegetation in late summer. The nest itself is similar to the nests of Chipping Sparrow, which are almost entirely constructed with grasses. One difference between the two is that Field Sparrows tend to use a lesser variety of grass types and less animal hair in the nest lining.

Field Sparrow nest site

The nest is located in a main fork within the crown of an as yet unidentified shrub/sapling. This plant would not not have been suitable for nesting in late spring/early summer as it would would have been exposed to predators in the absence of developed vegetation around it that has now provided dense cover.

Field Sparrow nest habitat

This shot of the nest site taken further back shows its position relative to our access trail. The habitat would be best described as a grassy clearing between dense deciduous forest and a large peat bog. To name a few, Yellow-throated Vireo, Scarlet Tanager and Yellow-billed Cuckoo sang from the forest edge throughout the summer, Swamp Sparrow, Common Yellowthroat and Wilson’s Snipe occupied the bog, while Eastern Towhee shared the sunny gap with Field and Song Sparrows.

Fledgling at Rock Ridge in early July

Fledgling and juvenile Field Sparrows have been encountered throughout the summer period across the study area. This area, with its countless rock outcrops and old fields, has been and continues to be an important region for Field Sparrows in Ontario. The retreat of the glaciers left extensive areas of bare rock and/or shallow vegetation resistant soils, providing open areas for Field Sparrows to prosper. It is plausible however that the suppression of fires, natural succession of fields and conversion to intensive agricultural methods will continue to reduce their numbers in Ontario and beyond.

the Nest Files – Eastern Phoebe

Eastern Phoebe nest contents

Eastern Phoebe (Sayornis phoebe)

Nidiologicals (from Peck and James 1987)

Habitat=deciduous and mixed woodlands; rural areas
Microhabitat=primarily man made structures in open forested habitats but also in natural crevices and ledges
Spring arrival=April
Average nest height=2.1-3m
Nest builder=female
Average # of broods/season=1-2
Average Egg Date=May 23-June 18
Area sensitive=no
Average clutch size=4-5
Incubation period=14-15 days
Egg colour=white with some of the clutch speckled
Parasitized by cowbirds=yes

Guard duty-male Eastern Phoebe

[This is a pre-scheduled post written with haste on June 30 for publishing on July 3. We are hoping to have internet back up and running by the end of the weekend]

This Eastern Phoebe nest was originally built in a prior year, probably 2008, and was re-established by the adult male (above) and female (below) beginning June 17, 2009. The pair began checking out the dilapidated nest found under an eave on top of a motion-sensor light in mid-June. A day or two later, an adult was seen carrying material to the nest. Eastern Phoebes are remarkably tolerant of human activity around their nests and this particular pair is no exception as dogs, cats, people and various vehicles come and go without any apparent objection to the birds. By June 21, the nest was refurbished with a tidy new wreath of moss, plant fibers and animal hair. Upon checking the nest with a mirror on June 22, two eggs were discovered which became four by June 24. The female has been incubating ever since.

Adult Eastern Phoebe incubating

This species has a variable incubation period, however the average is 14-15 days, which would mean that the eggs should hatch around the end of the first week of July. We will keep an eye on this nest for as long as we can with the hope that we might determine its final outcome.

the Nest Files – Ovenbird

Male Ovenbird banded at MABO (early June)

Ovenbird (Seiurus aurocapillus)

Nidiologicals (from Peck and James 1987 and Van Horn 1994)

Habitat=deciduous forests
Microhabitat=nest built in sparsely vegetated forest floor with dense leaf litter, often in forest clearings
Spring arrival=May
Average nest height=ground
Nest builder=female
Nest building period=5 days
Average # of broods/season=1 (rarely 2)
Average Egg Date=June 6-June 20
Area sensitive=yes
Average clutch size=4-5
Incubation period=12 days
Egg colour=white with speckles of gray, brown or hazel forming a wreath at large end
Fledgling stage=young leave nest 8-10 days after hatching
Parasitized by cowbirds=yes

The Ovenbird is a common species inhabiting both dry and mesic deciduous forest types throughout our study area in the northern Frontenac Arch. Our point counts suggest that they are one of the most abundantly occurring species in contiguous tracts of deciduous and mixed forest, both mature and younger stands, where the understorey is sparsely developed and canopy closure is high. The Ovenbird, a ground specialist, is an area sensitive species, which means that productivity is adversely affected by forest fragmentation. Data from the Breeding Bird Survey and the Ontario Breeding Bird Atlas indicate a significant population decline in southern Ontario where most large tracts of forest have been reduced to isolated smaller fragments unsuitable for reproduction of this species. The Ovenbird winters in southern Florida, Mexico, Central America and the Caribbean islands.

Nest contents

This Ovenbird nest was discovered at our Maplewood Bog MAPS station on June 14, 2009. This species is notoriously cryptic in its habits during the breeding season, often walking slowly along the forest floor to its well concealed nest. The species gets its name for its domed nest that resembles an oven. I was rather exstatic to find this nest as I had spent a good few hours tracking adults in two other territories in nearby Frontenac Park, both of which led me to recently fledged young instead of active nests. The eggs are heavily speckled with reddish-brown marks that are concentrated at the larger end.

The Oven nest

So here is the weird part. The nest was built at some point between our first and second visit to MABO in a 12m long net lane that was cleared in late May! The female will only flush from the nest if your foot comes to within perhaps 10 inches or so of the nest, which is an extreme example of an incubating bird “sitting tight” to avoid exposing the nest to an intruder. It was remarkable that we hadn’t either stepped on the nest or flushed the female earlier that morning as the nest is almost directly in the middle of our foot path for checking the net.


It was only when I took the net down at the end of the day that I sensed that something small and quick had just dashed from the ground near my feet. I then had a quick look around in the thicker ground cover but didn’t find anything resembling a nest. I then turned to a small and rather odd looking clump in the grass underneath a juniper seedling and noted the classic domed shape of an Ovenbird nest and then four eggs! The nest is not unusual in being located in a clearing but it is unusual to be positioned in such an exposed context with direct sun beaming on its roof during late morning and much of the afternoon. There is however, a decent layer of dead leaves, which female Ovenbirds key on for nest site selection.


This last photo shows the location of the nest within the net lane and the habitat of choice for this particular pair of Ovenbirds. Incidentally, we captured presiding male and female in the net that goes here on the first net check of visit three! They both seem to be doing well as the male sings throughout the morning, no less than 30m from the nest at any time and the female incubates the four eggs despite our comings and goings. We won’t be revisiting MABO until next week, which will give these expecting parents some quality alone time to take care of business.

the Nest Files – Chipping Sparrow

Chipping Sparrow (S.Leckie)

Nidiologicals (from Peck and James 1987 and Middleton 1998)
Chipping Sparrow (Spizella passerina)

Habitat=open woodlands, parkland and treed fields
Spring arrival=April-May
Average nest height=0.9-2.4m
Nest builder=female
Average # of broods/season=2 (rarely 3)
Average Egg Date=June 4-June 20
Area sensitive=no
Average clutch size=4
Nest building period=~4 days
Incubation period=10-11 days
Microhabitat=high variable across geographic range; strong preference for conifers.
Egg colour=sky blue (rarely white) with irregular streaks, blotches and spots mostly at larger end
Parasitized by cowbirds=yes

Nest searching in the FBS study area has been generally productive, although we’ve been forced to reduce the amount of time for dedicated searching due to time constraints in June. I’ve been monitoring about forty nests in the last two weeks and have been pleased with success thus far in finding nests at a good rate when time is available. Yesterday in two hours, I was able to find active nests of Blue Jay, American Robin, Eastern Wood-Pewee, Baltimore Oriole and American Redstart. This post is an in-depth profile of Frontenac nesting species number three (only about 190 to go!).

The Chipping Sparrow is one of North America’s most abundant songbirds, a species that has benefited from the creation of suitable habitat by human settlement and infrastructure from Newfoundland to Alaska through Central America. Unlike most sparrows, the Chipping Sparrow prefers open woodlands and treed edges of waterways and fields. They seem to occur in higher densities in urban settings than undisturbed habitats. I recall my surprise in encountering an abundance of Chipping Sparrows in taiga habitats near the treeline in the Northwest Territories where Chipping Sparrows nested on the ground or slightly elevated in spruce saplings. Here in the Frontenac Arch, “chippers” are abundant in most areas where natural or man-made forest clearings occur. Our point counts are revealing a strong preference for mixed forest sites containing Eastern White Pine and/or juniper.

Chipping Sparrow nest contents (Derbyshire)

This Chipping Sparrow nest was discovered in Frontenac Provincial Park in early June within transitional habitat from young deciduous forest to mixed forest/rock barren. I was alerted to the presence of the nest by alarm calling adults. The nest was easily found at the outer end of a low pine bough, not terribly well hidden. The nest itself is a loosely formed cup consisting of dried grass with a more densely formed inner bowl of animal hair and fine plant fibers. The four eggs are a distinctive sky blue with irregular dark markings, mostly at the larger end. It was recently discovered that male Chipping Sparrows copulate with multiple females in neighboring territories (extra-pair copulations).


These last three shots visually describe the nest position and the habitat. It is unusual for a Chipping Sparrow to select such an exposed location for the nest as this particular one is clearly visible from the sides and especially from below. Not surprisingly, the preference of Chipping Sparrows for wooded edges has exposed them to high rates of brood parasitism by Brown-headed Cowbirds. Interestingly, of the forty nests (all species) I have discovered thus far, I have yet to find a single case of parasitism. This is, in part, due to the habitat where nests have been found, interior forest sites where cowbirds are rare. I have begun nest searching in a forest plot adjacent to open habitats and will be interested to observe any divergence in rates of parasitism.

Nest position (Derbyshire)

Nest site (Derbyshire)