Patch Scale Nest-Site Selection by Marbled Murrelets (Brachyramphus marmoratus)

Abstract

ABSTRACT. The Marbled Murrelet (Brachyramphus marmoratus) is a threatened alcid that nests almost exclusively in old-growth forests along the Pacific coast of North America. Nesting habitat has significant economic importance. Murrelet nests are extremely difficult and costly to find, which adds uncertainty to management and conservation planning. Models based on air photo interpretation of forest cover maps or assessments by low-level helicopter flights are currently used to rank presumed Marbled Murrelet nesting habitat quality in British Columbia. These rankings are assumed to correlate with nest usage and murrelet breeding productivity. Our goal was to find the models that best predict Marbled Murrelet nesting habitat in the ground-accessible portion of the two regions studied. We generated Resource Selection Functions (RSF) using logistic regression models of ground-based forest stand variables gathered at plots around 64 nests, located using radio-telemetry, versus 82 random habitat plots. The RSF scores are proportional to the probability of nests occurring in a forest patch. The best models differed somewhat between the two regions, but include both ground variables at the patch scale (0.2-2.0 ha), such as platform tree density, height and trunk diameter of canopy trees and canopy complexity, and landscape scale variables such as elevation, aspect, and slope. Collecting ground-based habitat selection data would not be cost-effective for widespread use in forestry management; air photo interpretation and low-level aerial surveys are much more efficient methods for ranking habitat suitability on a landscape scale. This study provides one method for ground-truthing the remote methods, an essential step made possible using the numerical RSF scores generated herein.RÉSUMÉ. Le Guillemot marbré (Brachyramphus marmoratus) est un Alcidé menacé qui niche presque exclusivement dans les vieilles forêts de la côte nord-américaine du Pacifique. L'étude de son habitat de nidification exige des ressources financières importantes. En effet, les nids de guillemots sont très difficiles à trouver, de sorte que cette activité est coûteuse, conférant à la planification de l'aménagement et à la conservation un caractère incertain. Les modèles fondés sur des cartes du couvert forestier provenant de la photointerprétation ou encore sur des évaluations faites à partir de vols en hélicoptère à basse altitude sont actuellement utilisés pour classer l'habitat de nidification des Guillemots marbrés en ColombieBritannique en fonction de sa qualité présumée. Cette approche repose sur la présomption que ce classement est corrélé à l'occupation des nids et à la productivité des guillemots. L'objectif de cette étude était de déterminer les meilleurs modèles pour prévoir l'habitat de nidification des guillemots dans la partie accessible au sol des deux régions étudiées. Nous avons élaboré des fonctions de sélection des ressources (FSR) au moyen de modèles de régression logistique, à partir de variables de peuplements forestiers récoltées a...

Factors affecting reproduction of WoodpigeonsColumba palumbusin North African forests: 1. Nest habitat selection

“…The attraction of Woodpigeons for taller trees has often been reported , Rouxel & Czajkowski 2004, although this has been virtually unstudied quantitatively. Tall trees may permit escape from human persecution (Dutta 2007, Hanane & Baâmal 2011 and may also provide a distinct landmark to help commuting adults in locating the nest (Silvergieter & Lank 2011). Furthermore, the presence of livestock (sheep and goats) seems to affect the selection of nest-tree by Woodpigeons in the study area.…”

“…Nest-site selection by birds results from a series of behavioural choices (Silvergieter & Lank 2011). Nestsites in birds may offer the basic needs of breeding adults, eggs and young, including a suitable substratum, protection from inclement weather (Sadoti 2008) and predators (Hatchwell et al 1999), and proximity to food sources (Wiehn & Korpimäki 1997).…”

Marbled Murrelet nest site selection at three fine spatial scales

“…At the patch level, Manley (1999) found no evidence of selection for the size or types of gaps in a patch. Other researchers have found measures of vertical complexity to be positively related to likelihood of nesting (Conroy et al 2002, Waterhouse et al 2002, Silvergieter and Lank 2011a, numbers of occupied behaviors observed Newsom 2002, Burger andBahn 2004), and likelihood of occupancy (Hamer et al 2008).…”

“…One radio-telemetry study examined the difference between successful versus unsuccessful nests (Bradley 2002) at a landscape scale. Although landscape scale habitat data may be easier to obtain, landscape-only models received less support compared with models that incorporated patch scale variables measured from the ground (Silvergieter and Lank 2011a). Several other habitat preference studies used number of murrelet detections from ground surveys to make comparisons at the stand scale (Miller and Ralph 1995, Burger and Bahn 2004, COSEWIC 2012.…”

“…Studies that examined murrelet habitat preferences at smaller scales were only able to offer comparisons of known nest sites to random sites, without verification that murrelets had not nested at random sites (Baker et al 2006, Golightly et al 2009, Silvergieter and Lank 2011a, b, Wilk et al 2016. Verification is difficult because the only way to be certain that a forest patch or tree was not used for nesting is to climb all trees at a random site and inspect each branch or deformity for evidence of nesting.…”