the Nest Files – Ovenbird

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Male Ovenbird banded at MABO (early June)

Ovenbird (Seiurus aurocapillus)

Nidiologicals (from Peck and James 1987 and Van Horn et.al 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
Incubation=female
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.

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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.

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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.

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microhabitat

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.

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habitat

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.

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