Variation in the timing of reproduction and clutch size of Afrocanarian blue tits Cyanistes teneriffae ultramarinus in the Saharan Atlas of Algeria Ala-Eddine ADAMOU 1,2, Mohamed KOUIDRI 1,2, Anna BAŃBURA 3, Mohamed Laïd OUAKID 4, Yassine CHABI 4 and Jerzy BAŃBURA 5* Département d’Agronomie, Faculté des Sciences, Université Amar Telidji, B.P. 37, Laghouat, Algérie Equipe désertification et climat, Laboratoire Mécanique, Université Amar Telidji, B.P. 37, Laghouat, Algérie 3 Department of Health Psychology, Institute of Psychology, Ingardena 6, 30-060 Kraków, Poland 4 Department of Biology, Faculty of Science, Badji Mokhtar University, B.P. 12, Annaba, Algeria 5 Department of Experimental Zoology and Evolutionary Biology, Faculty of Biology and Environmental protection, University of Łódź, Banacha 12/16, 90−237 Łódź, Poland, *e-mail:
[email protected] (corresponding author) 1 2
ARTICLE INFO published in Pol. J. Ecol. (2015) 63: 599–607 received after revision September 2015 doi 10.3161/15052249PJE2015.63.4.012 key words Afrocanarian Blue Tits marginal populations Algerian highlands life history laying dates clutch size
ABSTRACT We examined the variation in the date of the onset of egg laying and clutch size in three peripheral populations of the Afrocanarian Blue Tits Cyanistes teneriffae ultramarinus at the edge of the species and subspecies geographic range. This study was carried out in three study sites, 130−290 km apart, in similar geographic conditions of the South Border Range of the Saharan Atlas in Algeria. Mean altitudes of nesting territories were between 1327 and 1437 m a.s.l. Habitats of the study sites were covered by the secondary, human-modified vegetation, ranging from a maquis shrubland, with the Holm oak Quercus ilex shrubs to woodlands dominated by the Atlas cedar Cedrus atlantica or by the Aleppo pine Pinus halepensis. 169 wooden nest-boxes were monitored for breeding parameters (laying dates and clutch sizes) during the breeding seasons 2007−2009 and 2011−2013. The timing of egg laying was relatively late for the latitude of the study sites, with overall mean laying dates varying between the study sites from 4 to 13 May. The laying date was influenced by the altitude of nesting sites, with the dates being delayed with increasing altitude. Overall mean clutch size differed between the study sites from 5.91 at Djelfa to 8.43 at Aflou. Clutch size tended to decrease with the advance of the breeding season. Because the study populations inhabit areas of similar physical conditions (climate and altitude), the main inter-population source of variation in the breeding parameters studied was probably variation in habitat quality.
Large-scale geographic variation in lifehistory traits of birds usually shows consistent latitudinal and less clear longitudinal patterns, resulting from systematically differing selection pressures (L ack 1947, O wen 1979, Sanz 2002, Farga l lo 2004, Møl ler et al. 2014a, b). In the case of bird species that have wide, often continental-scale, geographic ranges, with some variation in habitat preferences, peripheral populations are often unstable and their life-history characteristics deviate from typical geographic patterns (Sl agsvold 1981, R ap op or t 1982, Jar v inen 1986, Farga l lo 2004, B ar r ientos et al. 2009). This results
from the fact that inland borders of species geographic ranges are usually set by some kind of physical barriers, such as mountain ranges, deserts or river valleys, with the areas closing to the borders being characterized by especially harsh and variable physical conditions (R ap op or t 1982, Jar v inen 1986). If peripheral areas include mountains, also elevational changes in physical and ecological conditions, which tend to be more variable than in lowland, affect life histories of animals (R ap op or t 1982, Hi l le and C o op er 2015). In most Western Palearctic species of insectivorous birds laying dates are delayed
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and clutch size increases with latitude (L ack 1947, 1950, O wen 1977), but at least in some cases variation in both these properties is especially high in the South (Is enmann 1987, Blondel et al. 1993, Farga l lo 2004). For the Blue Tit Cyanistes caeruleus, Farga l lo (2004) found that the simple linear relation between the latitude and laying date may be shown only for the latitudes higher than ca 42°N, while below this value, both very earlybreeding and late-breeding populations exist. An analogous tendency for clutch size is also curvilinear, with wide variation for the whole range of latitudes (Farga l lo 2004). For both these life-history parameters, the most important modifying factors proved to be altitude and the type of habitat (Farga l lo 2004). In this study we focus on laying dates and clutch sizes in truly marginal continental populations of Afrocanarian Blue Tits Cyanistes teneriffae ultramarinus at the edge of the subspecies and species geographic range; an even more peripheral population occurs in Libya (Cramp and Per r ins 1993, Hanss on et al. 2014, G oh li et al. 2015). After G oh li et al. (2015), but unlike G osler et al. (2013), Møller et al. (2014a, b) and some other authors, we consider Afrocanarian Blue Tits as a separate species closely related to the Blue Tit. Biogeographically, the area of our study belongs to the Saharo-Arabian region of the Western Palearctic (Blondel and Arons on
1999) and constitutes peripheral area of geographic ranges of many different organisms for which the Sahara Desert is an impassable barrier (R ap op or t 1982). It was long known that Blue Tit populations living in this area, like other Mediterranean and Canary Island populations, differ in habitat selection from continental European Blue Tit populations (Snow 1954). In most of continental Europe and in Britain, Blue Tits inhabit various deciduous forests and woody habitats, while Afrocanarian Blue Tits often nest in montane woodlands, including coniferous and evergreen forests (Snow 1954). Actually, in the region of our present study, breeding habitats of Afrocanarian Blue Tits are confined to mountain and highland remnants of forests, highly degraded by humans and very close to and under the great influence of the Sahara Desert. There were some other studies on life-histories of Algerian Afrocanarian Blue Tits (i.e. C habi et al. 1995, 2000, C habi and Is en man n 1997, Mo a li and Is en man n 1990, Z i ane et al. 2006, Br a h m i a et al. 2013), but they were carried out in coastal regions of North Algeria. The most important idea of this study was that populations of Afrocanarian Blue Tits inhabiting degraded patches of woodland habitats in the montane areas at the border of the species geographical range should display exceptional characteristics of breed-
Fig. 1. The Aflou, Djelfa and Batna study sites at the edge of the Blue Tit species complex geographic area (shaded).
Breeding biology of Afrocanarian Blue Tits
ing performance, different from non-marginal populations. Since physical and ecological conditions of living in the study area are unstable and highly variable, probably resulting in trophic conditions changing in differing directions and in changing mortality rates, we predict that the timing of breeding and clutch size should show some consistent spatiotemporal and elevation-dependent patterns. Especially, we expect that laying dates should be relatively late and clutch size relatively large. Therefore, we examine variation in laying dates and clutch sizes in three peripheral populations, at study sites located more than 100 km apart. We chose 3 study sites to represent generally similar geographical conditions of the South Border Range of the Saharan Atlas in Algeria, constituting the edge of the Afrocanarian Blue Tit geographical range (Fig. 1) (Cramp and Per r ins 1993, Hanss on et al. 2014, G oh li et al. 2015). The sites represent rural habitats and are inhabited by peripheral populations of the Afrocanarian Blue Tit. The most south-westerly site is located near Aflou (34°12′N, 02°11′E, mean altitude 1407 m) – maquis and remnants of a forest, with the Holm oak Quercus ilex as a dominant shrub species (density 56.6 per ha), with an admixture of the Mt. Atlas mastic tree Pistacia atlantica, and Juniperus oxycedrus and Juniperus phoenicea as main bush species (own data). A little more easterly site is located near Djelfa (34°38′N, 03°09′E, mean altitude 1328 m a.s.l.) – a coniferous forest, with Aleppo pine Pinus halepensis as a dominant tree species (274.1 per ha), the Holm oak as a severely declining species reduced to the understory layer, and with the same 2 species of Juniperus occurring (own data). A still further northeasterly site is located near Batna (35°35′N, 06°03′E, mean altitude 1437 m) – a forest dominated by the Atlas cedar Cedrus atlantica (113.2 per ha), with Holm oaks, Ash trees Fraxinus communis and Juniperus oxycedrus in the understory (own data). In general vegetation in the whole region, including the study sites, having been under strong human pressure for more than 5 thousand years, is greatly degenerated (Blondel and Arons on 1999, D j ema and Mess aoudene 2009), so that there are only patches of habitats suitable for nesting Tits.
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Climatic conditions of all three sites are similar, with cool winters and warm summers, mean yearly temperatures 11−15°C, precipitation 300−350 mm, and de Martonne aridity index 11.9−14.6, suggesting semi-arid status of the area (D o e r r 1962). The sites face the Sahara Desert with only some transitory areas of separation. The study was carried out in 2007−2009 at Batna and Aflou and in 2011−2013 at Djelfa. During winters preceding the studies, we set up wooden nest-boxes on the trunks of trees at the height of 3−4 m: 90 at the Batna study site, 38 at Djelfa and 31 at Aflou − all the nest-boxes were checked for their occupation by tits. The nest-box occupation rate by Blue Tits was 40% at Batna, 26% at Djelfa and 71% at Aflou with respect to the nest-boxes available. At the Batna site, nest-boxes were also occupied by Great Tits, but not by Coal Tits that occurred at the site as well. At both the Djelfa and Aflou study sites, nest-boxes were only occupied by Blue Tits, even if Great Tits and Coal Tits occurred at Djelfa, whereas they were completely absent from Aflou. Nest-boxes were inspected at least twice a week during the breeding season (AprilJune) to record the date of the onset of laying and clutch size. If not recorded directly, the first egg laying date was calculated, assuming that one egg was laid per day (C r amp and Pe r r ins 1993). Only complete clutches were included in this study. As complete clutches we considered those that no longer increased and started to be incubated by females In our statistical analyses we took into account the small sample sizes in Aflou and Djelfa study sites (applying relatively robust methods and conducting only selected comparisons). Linear mixed models were applied to test laying dates and clutch sizes in relation to different independent variables and factors (We st et al. 2015). We tested laying dates for differences between study sites with respect to the altitude of nesting territories, treating year as a random factor (subject). We also tested the relation between the laying date and altitude, while treating both the year and site factors as random factors. Clutch size was examined for inter-site variation with respect to laying date and altitude, with year being treated as a random factor. Linear mixed models were constructed using
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restricted maximum likelihood estimates and approximating degrees of freedom by the Sattertwaite method (West et al. 2015). We used general linear models to compare laying dates and clutch sizes between the Batna and Aflou Blue Tit populations. In these models we treated year and site as fixed factors and used respective covariates, such as altitude and laying date in the case of clutch size and altitude when the laying date was the explained variable. We calculated Pearson’s correlations between clutch size and laying date. In this analysis, individual values of clutch size and laying date were centered by subtracting a within-site-within-year mean from them, with correlations being calculated both for all study sites pooled and treated separately. All statistical calculations were performed using IBM SPSS Statistics 22 software. The timing of breeding was considerably variable in the study populations of the Afrocanarian Blue Tit. Laying dates tended to be earliest in Aflou, intermediate in Djelfa and latest in Batna (Table 1). In general the onset of egg laying differed between the study sites and was positively associated with altitude of territory locations, but the relationship differed between the study sites (Table 2). We also found high year-to-year effect on variation in laying dates, usually concurring with the effect of altitude, within the study sites (GLM: F2;28 = 4.95, P = 0.016 year effect and
F1;28 = 2.94, P = 0.1 altitude effect in Aflou, F2;18 = 16.07, P
