VOLUME 12, ISSUE 2, ARTICLE 1 Deeming, D. C., L. E. Biddle, and C. R. Du Feu. 2017. Interspecific and intraspecific spatial separation by birds breeding in nest boxes. Avian Conservation and Ecology 12(2):1. https://doi.org/10.5751/ACE-01026-120201 Copyright © 2017 by the author(s). Published here under license by the Resilience Alliance. Research Paper Interspecific and intraspecific spatial separation by birds breeding in nest boxes Denis C. Deeming 1, Lucia E. Biddle 1 and Christopher R. du Feu 2 1University of Lincoln, 2Treswell Wood Ringers Group ABSTRACT. Nest boxes can be seen as a conservation tool for improving low-grade nesting habitat but it is unclear how sympatric species using boxes establish a spatial distribution relative to conspecifics and heterospecifics. This study determined the distances between nest boxes occupied by Blue Tits (Cyanistes caeruleus) and Great Tits (Parus major) in two British woodlands to ascertain whether spatial distribution was affected by species and, if it was, whether there were reproductive consequences of this breeding distribution. Occupancy of nest boxes at two woodland sites were recorded on an annual basis between 2010 and 2014, inclusive. Distances between nest boxes, and reproductive activity, were recorded. Even if nest boxes showed a clumped distribution in the woodlands, the occupancy of the boxes was random. Not all boxes were used and the minimum distance between occupied boxes was at least twice the distance between boxes in general. Blue Tits tended to have greater distances between boxes containing conspecifics but distances between boxes containing heterospecifics were generally of comparable lengths. Reproductive output was only affected in relation to clutch size for Blue Tits nesting at one site. Nest boxes that aim to improve habitats that lack suitable nesting sites should be placed to reflect actual dispersal distances of the focal bird species. Séparation spatiale interspécifique et intraspécifique d'oiseaux nichant dans des nichoirs RÉSUMÉ. Les nichoirs peuvent être considérés comme des outils de conservation pour améliorer les milieux de nidification de mauvaise qualité, mais on ne sait pas comment les espèces sympatriques utilisant les nichoirs établissent une répartition spatiale relativement aux individus conspécifiques et hétérospécifiques. La présente étude avait pour but de déterminer les distances entre les nichoirs occupés par les Mésanges bleues (Cyanistes caeruleus) et les Mésanges charbonnières (Parus major) dans deux boisés britanniques afin de vérifier si la répartition spatiale était influencée par les espèces et, le cas échéant, s'il y avait des conséquences sur le plan reproductif de cette répartition de nidification. L'occupation des nichoirs à deux sites boisés a été colligée annuellement de 2010 à 2014 inclusivement. La distance entre les nichoirs et l'activité reproductrice ont été notées. Même si les nichoirs montraient une répartition groupée dans les boisés, leur occupation était aléatoire. Tous les nichoirs n'étaient pas occupés et la distance minimale entre deux nichoirs occupés était au moins le double de celle entre les nichoirs en général. Chez la Mésange bleue, les distances entre les nichoirs occupés par des individus conspécifiques étaient plus grandes, mais les distances entre les nichoirs occupés par des individus hétérospécifiques étaient généralement de longueurs comparables. La seule composante affectée du succès reproducteur était la taille de ponte de la Mésange bleue nichant à un site. Les nichoirs dont l'objectif est d'améliorer l'habitat là où il manque de sites de nidification propices devraient être installés pour refléter les distances de dispersion réelles des espèces d'oiseaux ciblées. Key Words: Blue Tit; Great Tit; nearest neighbor distances; nest box; reproductive success INTRODUCTION sites in many woodland locations (Newton 1994, Camprodon et Provision of nest boxes is a conservation measure by which al. 2008, Mazgajski 2009, Cockle et al. 2011). Artificial provision habitats can be made attractive to species for breeding (Mänd et of nest boxes may allow species to breed in habitats that may be al. 2005, Sánchez et al. 2007, Lima and Garcia 2016). For instance, suitable for various ecological reasons, such as suitable foraging forestry management often removes dead or decaying trees, which opportunities, but lack appropriate natural nest sites (Newton can develop natural cavities, or provide sites for cavity excavation 1994, Sánchez et al. 2007). Provision of nest boxes can allow an by species such as woodpeckers (Picidae; Remm et al. 2006, increase in breeding density in some, but not all, habitats (Mänd Sánchez et al. 2007). The absence of large diameter trees can also et al. 2005, Camprodon et al. 2008). However, provision of nest limit availability of natural cavities (Camprodon et al. 2008). boxes can also lead to an ecological trap because birds may be These serve as nest sites for secondary cavity-nesting species, i.e. “tied” to breeding in a suboptimal habitat (Mänd et al. 2005, Klein species that utilize existing holes rather than excavating their own, et al. 2007, Rodríguez et al. 2011). although holes created by woodpeckers or other primary cavity In Europe, foraging competition between Eurasian Blue Tits excavators can be durable but eventually the wood can decay and (Cyanistes caeruleus; hereafter Blue Tits) and Great Tits (Parus the cavity is lost (Cockle et al. 2011). Hence, for natural and major) in woodland habitats can be minimized by use of different human-induced reasons there can be a shortage of suitable nest parts of the habitat (Colquhoun and Morley 1943). However, use Address of Correspondent: Denis C. Deeming, School Of Life Sciences, University of Lincoln, Lincoln , United Kingdom, LN6 7DL, [email protected] Avian Conservation and Ecology 12(2): 1 http://www.ace-eco.org/vol12/iss2/art1/ of cavities for nesting can depend on the availability of suitable METHODS natural or primary excavator cavities (Newton 1994, Camprodon et al. 2008, Mazgajski 2009, Cockle et al. 2011). If such sites are Locations few in number in any particular location then artificial boxes may Riseholme Park campus, University of Lincoln (53°16′N, 0°31′ offer a suitable nest cavity and allow breeding (Sánchez et al. 2007, W) has eight small interconnected areas of mainly deciduous Camprodon et al. 2008, Lima and Garcia 2016). The locations of woodland (ranging from 0.6 to 5.8 ha adding to a total of 16 ha) a population of nest boxes are chosen by humans, which may not and dominated by beech (Fagus sylvatica), ash (Fraxinus reflect the most appropriate habitat for the different species of excelsior), and sycamore (Acer pseudoplatanus) surrounded by birds (Mänd et al. 2005, Milligan and Dickinson 2016). arable farmland (Britt and Deeming 2011, Deeming 2013). Given that both Blue Tits and Great Tits are sympatric the Between 70 and 80 nest boxes (mainly with base dimensions of question arises of whether intraspecific or interspecific 115 mm × 140 mm and minimum height of 155 mm, although competition determines the spatial separation of breeding birds around 10% were larger in base area) were available during 2010 within nest boxes provided within the habitat. Nest box occupancy to 2014 for Blue Tits and Great Tits to use (range of densities = shows a positive correlation with breeding bird density in both 4.25-5.00 boxes per ha; Table 1). Boxes were typically positioned Blue and Great Tits (Minot and Perrins 1986). In Great Tits on the north sides of trees at a height of 1.5–1.8 m from the distances between boxes were affected by bird density: lower ground. The number of boxes varied slightly between years density increased the distances between nest boxes containing because of damage and loss of boxes and addition of boxes. conspecifics (Krebs 1971). However, Green (1979) argued that Placement of boxes allowed provision of potential nesting sites although intraspecific interference was significant for both Blue over most of the woodland. Nest boxes were monitored on a Tits and Great Tits, if interspecific interference occurred then it weekly basis during each breeding season to record the presence would be relatively small. of a nest, the species concerned, and the reproductive output from the nest (clutch size, brood size, and number of fledged nestlings). From a conservation perspective the number of nest boxes will Most boxes were occupied each year by Great Tits or Blue Tits determine how widely they are dispersed within the available but one or two boxes a year were occupied by Winter Wren habitat, especially if they are placed to achieve maximum coverage (Troglodytes troglodytes), Coal Tit (Poecile ater), European Robin through the available area. Be it a box, or a tree hole, the birds (Erithacus rubecula), or Eurasian Treecreeper (Certhia familiaris; are unable to move the location of a cavity. Whether any cavity is for exact numbers see Table 1). occupied may depend on where it lies adjacent to any breeding territory if there is a need to minimize intraspecific interference Treswell Wood, near Retford, Nottinghamshire, UK (53°18′N, 0° (Gosler 1993). Building and locating nest boxes is not without 51′W) is a Nottinghamshire Wildlife Trust reserve of 47 ha of cost and so conservation schemes might be more cost-effective if mixed woodland dominated by ash with hazel (Corylus avellana) there is efficient placement of boxes. Nest boxes are often provided and surrounded by farmland (Deeming and du Feu 2011, in excess because rarely are all boxes occupied (e.g., Mänd et al. MacColl et al. 2014). The number of boxes varied from 173 to 2005) but it is unclear whether this reflects the carrying capacity 204 over the time period studied (range of densities = 3.68-4.34 of the habitat or the suitability of location for nest boxes. No boxes per hectare; Table 1); they varied in style from standard nest studies have yet investigated whether the numbers and boxes through to custom built cavities excavated out of tree distribution of nest boxes could be better managed to maximize stumps (du Feu 2003).