Barbara Frei

Carleton University

B.Sc. Honours

Biology

2005

McGill University

M.Sc.

Natural Resource Sciences

2009

McGill University

Ph.D.

Natural Resource Sciences

2014

Postdoctoral research scholarship

Fonds de recherche Nature et Technologies

Postdoctoral research scholarship

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Interspecific competition and nest survival of the threatened Red-headed Woodpecker

The cavity-nesting Red-headed Woodpecker (Melanerpes erythrocephalus) is a once common, but now threatened, species across most of its range. Although several drivers for the species’ decline have been suggested, few have been quantitatively tested and still little is known of the Red-headed Woodpecker’s breeding ecology. From 2010 to 2011, we monitored 60 Red-headed Woodpecker nests across a variety of habitats in southern Ontario to estimate the species’ nest survival near the northern edge of their range where populations are rapidly declining. We investigated the relevance of a suite of meteorological, biotic, temporal, and habitat-based drivers on woodpecker nesting success. The frequency of European Starlings (Sturnus vulgaris) sightings near active woodpecker nest sites was the strongest factor influencing Red-headed Woodpecker nest survival. Logistic-exposure nest success assuming constant survival (68 %) dropped significantly (to 13 %) when the frequency of Starling sightings was considered. More than a third of nest failures were suspected to be the result of aggressive cavity takeovers by Starlings, and nests with Starlings present were almost four times more likely to fail than nests without. Red-headed Woodpecker nest survival early in the breeding season appeared depressed, perhaps as a result of interference competition with Starlings. Nesting success increased with the availability of snags and dead branches, which may increase foraging opportunities and parental attentiveness at the nest, leading to more effective nest defense. This research is contrary to previous reports that Starlings do not negatively affect North American primary cavity nesters, and demonstrates the importance of considering multiple ecological, temporal, and spatial factors when determining threats for species-at-risk.

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Maladaptive Habitat Use of a North American Woodpecker in Population Decline

Rapid anthropogenic habitat changes can lead to non-ideal habitat use by animals, often resulting in lower fitness and population declines. An extreme case of use and fitness mismatch is an ecological trap where habi- tat quality cues are disjointed from the true quality of the habitat. Species primarily associated with anthropogenically altered habitat, such as red-headed woodpeckers (Melanerpes erythrocephalus), may be especially vulnerable to use and fitness mismatch as they encounter novel environ- mental challenges. We investigated multi-scale habitat use and nesting success of red-headed woodpeckers to assess their vulnerability to mis- matches between use and fitness as a result of non-ideal habitat use across multiple scales. We found that habitat characteristics that promote feeding potential such as canopy openness and greater dead limb length appeared paramount and were consistent in use across several spatial scales although reproductive fitness suffered. This contrasts with the assumption that habi- tat use by nesting birds should instead favor predation avoidance at smaller scales to improve reproductive fitness and suggests that maladaptive, food- based habitat use by red-headed woodpeckers in southern Ontario may result in ecological traps for the species. Whether due to poor habitat choices or costly ones in favor of feeding potential, it is vital to consider this behavior in conservation and management plans for this and similar species. We suggest multi-scale habitat use studies that consider fitness outcomes are critical for species-at-risk in human-modified landscapes

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Low Fecundity of Red-Headed Woodpeckers (Melanerpes erythrocephalus) at the Northern Edge of the Range

The Red-headed Woodpecker (Melanerpes erythrocephalus) is a threatened bird species undergoing continued population declines across most of its range. Despite the conservation concern, there are few published studies on the species’ fecundity. We examined the nesting phenology, clutch size, and fledging success of Red-headed Woodpecker nests in southern Ontario and northern New York, where population declines are especially pronounced. We calculated the fecundity of the Red-headed Woodpecker populations from fledgling numbers and nest survival estimates. We found that nest phenology and clutch sizes were similar to those reported in other studies for the species. Red-headed Woodpecker nests monitored using video inspection had an unusually low fledging success (39%), and an average fecundity of 0.43 female fledglings per female per year. The fledgling success and fecundity for the monitored Red-headed Woodpecker population was lower than that reported by other published studies on Melanerpes spp., as well as for other genera of woodpeckers. The fecundity was also below the minimum threshold needed to offset mortality for the species, when compared to a majority of minimum fecundity values estimated from the literature. We suggest low fecundity for Red-headed Woodpeckers at the northern edge of their range may be the chronic condition of sink populations, or a more recent phenomenon for small populations approaching local extinction.

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