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SOMMAIRE

LXXXII. — 1. 2014

4 108. CONSEIL D’ADMINISTRATION (P.).– *La Société d’Études Ornithologiques de France a vingt ans. . . 4 109. LOVATY (F.).– L'importance du bois mort sur pied et des microsites pour la reproduction de la Mésange huppée Lophophanes cristatus : exemple dans une pinède de Pins maritimes Pinus pinaster de Charente-Maritime (France) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 111. MONTADERT (M.) & LÉONARD (P.).– Sur le front de colonisation : la Gélinotte des bois Tetrastes bonasia dans les Alpes-Maritimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 113. CLOUET (M.), REBOURS (I.), GONZALEZ (L.), KOBIERZYCKI (É.) & ETCHEBARNE (J.B.).– Observation des dortoirs de Vautours percnoptères Neophron percnopterus au Pays basque au cours de l’année 2013 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 114. HENRY (F.), MOURGUIART (P.) & RECARTE (J.).– La migration automnale de l’Alouette des champs Alauda arvensis dans le département des Landes : bilan de 16 années de baguage . . . . . . 4 115. GOAR (J.-L.) & CLOUET (M.).– L’Aigle royal Aquila chrysaetos dans les Corbières : variations du régime alimentaire et des paramètres de reproduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 116. BRO (E.), BRILLARD (J.-P.) & MILLOT (F.).– Impact des fortes pluies et du temps froid et humide sur le succès de la reproduction et l’abandon des pontes chez la Perdrix grise Perdix perdix.. . . . . . 4 117. KOPIJ (G.) & POLIT (M.).– Les variations saisonnières de la grandeur des pontes et de la réussite de la reproduction de l’Hirondelle rustique Hirundo rustica, en relation avec l'emplacement des colonies et le type de bâtiments agricoles occupés. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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18 26 71-72 73-75 76-80

CONTENTS 4 108. CONSEIL D’ADMINISTRATION (P.).– *Société d’Études Ornithologiques de France twenty years. . . . 4 109. LOVATY (F.).– Occurrence of dead wood and nest sites for nesting by the Crested Tit Lophophanes cristatus: a case study in a Seaside Pine Pinus pinaster forest in West France. . . . . . . . . . . . . . . . . . . . . 4 111. MONTADERT (M.) & LÉONARD (P.).– Hazel Grouse Tetrastes bonasia is an expanding species in the southern part of French Alps (Alpes-Maritimes, France). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 113. CLOUET (M.), REBOURS (I.), GONZALEZ (L.), KOBIERZYCKI (É.) & ETCHEBARNE (J.B.).– Night roosts of the Egyptian Vulture Neophron percnopterus in the Basque county in 2013 . . . . . . . . . . . . . . . . 4 114. HENRY (F.), MOURGUIART (P.) & RECARTE (J.).– The autumn migration of the Eurasian Skylark Alauda arvensis in the Landes county (Southwest France): results from a 16-year lasting ringing programme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 115. GOAR (J.-L.) & CLOUET (M.).– The Golden Eagle Aquila chrysaetos in the Corbières (Eastern Pyrenean Range, France): variation in diet and breeding data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 116. BRO (E.), BRILLARD (J.-P.) & MILLOT (F.).– Impact of heavy rains and wet cold weather on Grey Partridge Perdix perdix clutch desertion and breeding success. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 117. KOPIJ (G.) & POLIT (M.).– Seasonal variation in the clutch size and breeding success in the Barn Swallow Hirundo rustica, in relation to the colony location and type of farm buildings occupied.

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Société d’Études Ornithologiques de France - SEOF

19-26

NOTES ET ARTICLES COURTS 4 110. ADDENDUM : CLECH (D.) (2013).- BIBLIOGRAPHIE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 112. ISENMANN (P.).– *Alfred SCHIERRER (1927-2014). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 118. SMITH (P.), PÉREZ (N.), DERNA (R.), COLMÁN (A.), DEL CASTILLO (H.) & ÁLVAREZ (A.).– *Sur la présence du Tyran de Cayenne Myiozetetes cayanensis (Tyrannidae) au Paraguay. . . . . . . . . . . . . . 4 119. MAUMARY (L.).– *Première observation du Bécasseau de Bonaparte Calidris fuscicollis en Tunisie. . . 4 120. DELORME (Q.).– *Description d’un chant atypique de Locustelle luscinioïde Locustella luscinoides Savi, 1824 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Alauda

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Muséum National d'Histoire Naturelle

ALAUDA (nouvelle série) LXXXII. – 1 . 2014

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31-40 41-49 51-62 63-69

SHORT COMMUNICATIONS 4 110. ADDENDUM : CLECH (D.) (2013).- REFRENCES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 112. ISENMANN (P.).– *Alfred SCHIERRER (1927-2014). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 118. SMITH (P.), PÉREZ (N.), DERNA (R.), COLMÁN (A.), DEL CASTILLO (H.) & ÁLVAREZ (A.).– *On the presence of Rusty-margined Flycatcher Myiozetetes cayanensis (Tyrannidae) in Paraguay. . . . . . . 4 119. MAUMARY (L.).– *First record of the White-rumped Sanpiper Calidris fuscicollis for Tunisia. . . . . 4 120. DELORME (Q.).– *Two types of song were performed by a male Savi’s Warbler Locustella luscinoides on 7 May 2013 at a site (Challerange, Ardennes) in northern France . . . . . . . . . . . . . . . . . .

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Mésange huppée - Bois mort et reproduction

Volume 82 (1) 2014

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IMPACT OF HEAVY RAINS AND WET COLD WEATHER ON GREY PARTRIDGE Perdix perdix CLUTCH DESERTION AND BREEDING SUCCESS Elisabeth BRO(1), Jean-Pierre BRILLARD(2) & Florian MILLOT(1)

Impact des fortes pluies et du temps froid et humide sur le succès de la reproduction et l’abandon des pontes chez la Perdrix grise Perdix perdix. Nous avons étudié l’impact des conditions météorologiques sur le succès reproducteur de la Perdrix grise Perdix perdix, en particulier sur l’abandon des pontes. Pour ce faire, nous avons d’une part suivi par radiopistage quotidien 437 poules et environ 250 pontes, et d’autre part nous avons enregistré sur une base horaire les températures et précipitations locales grâce à des stations météo automatiques. Nos résultats soulignent l’influence indéniable des conditions météorologiques sur le succès reproducteur de cette espèce. Les différences importantes de succès reproducteur observées entre les sites d’étude sont associées à un « coup de froid » de deux semaines au moment des éclosions en 2010, à des pluies modérées associées à des températures minimales relativement fraîches en 2011. En revanche nous n’avons pas détecté d’effet sensible des fortes pluies sur l’échec des pontes, en particulier sur leur abandon. Ce point est discuté, notamment en relation avec les changements climatiques et la prédiction d’une augmentation de fréquence des événements de type violents. Dans ce contexte et bien que ces (1) (2)

Dessin Philippe Vanardois

changements ne soient pas maîtrisables en soi, nous suggérons d’étudier leurs effets, pour éventuellement les prendre en compte dans les stratégies de gestion en vue d’une exploitation durable des populations. Les données de terrain présentées peuvent s’avérer utiles à la paramétrisation des relations écologiques au sein d’un modèle démographique. Mots clés : Perdix perdix, Succès de la reproduction, Abandon de ponte, Conditions météorologiques. Key words: Perdix perdix, Breeding success, Clutch failure, Weather conditions.

National Game & Wildlife Agency (ONCFS), Research Department, BP 20, 78 612 Le Perray-en-Yvelines cedex, France. Fertil’avi (poultry production consultant), 10 rue du 8 mai, F-37 360 Rouziers de Touraine, France.

INTRODUCTION The reproductive success is an important parameter in population dynamics of Galliform species (TROUVILLIEZ et al., 1988). This is especially the case in the Grey Partridge Perdix perdix (e.g. AEBISCHER & POTTS, 1995; BRO et al., 2000a), a sedentary farmland species that has largely de-

clined during the second part of the XXth century (see reviews KUIJPER et al., 2009 and PEBCMS 2013). The breeding success of the Grey Partridge is influenced by a series of ecological factors, predator abundance (e.g. POTTS & AEBISCHER, 1995; TAPPER et al., 1996), invertebrate abundance (e.g. Rands 1985; BRO & PONCE-BOUTIN, 2004 and references therein) and weather conditions (e.g.

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52 BIRKAN & JACOB, 1988; POTTS, 2012). Climatic changes are thus likely to influence the breeding success and the population dynamics of this species and may be an additional driver of a further decline in the future, as discussed by MOSS et al. (2001) for the Capercaillie Tetrao urogallus. Predicted effects of the global climatic change are an increase of mean temperature and an alteration in rainfalls regime (GIEC, 2007; LARSEN et al., 2008); they that are already statistically confirmed in Europe. Two different kinds of changes are predicted: regular long-term trend at a global scale (e.g. temperature) on the one hand, extreme events at a local or regional scale (e.g. intensity and frequency of heat spells, rainfalls) on the other hand. These changes have already tangible effects on the phenology, the population dynamics, the communities’ composition and distribution of many animal and plant organisms throughout the world (see MØLLER et al., eds. 2010 for birds). Some avian species display clear modifications in their migration behaviour, suggesting that they can adapt to a certain extent to climate changes. On the contrary, some other bird species with a narrower distribution or lower adaptive abilities may be less flexible. In addition, birds are more likely to be able to track climate trends than an increase in the frequency of extreme events, as suggested by a recent study documenting the effects of the North Atlantic Oscillation on the Black Grouse (Tetrao tetrix) in the French Alps (BARNAGAUD et al., 2011). In this context, we investigated the impact of heavy rains on clutch failure (desertion) on the Grey Partridge using data from a large scale study conducted in 2010-2011 where nesting females were radiotracked. Rains were recorded locally using a weather station. 2010 and 2011 were globally two years with an exceptionally good reproductive success in north-central France (REITZ, 2013) but we observed contrasted breeding success and rainy events across study sites (BRO et al., 2013). Our objective was to quantify the amount of clutch failure, an important parameter in population dynamics (BRO et al., 2000a; POTTS, 2012) that could be attributed to heavy rains. We also examined some relationships between breeding success and rainfalls /

Alauda 82 (1), 2014 temperature in June and July and assessed the quality of fits. Ultimately we aimed to provide field data to parameterize predictive models.

METHODS Study sites The study was carried out on 13 sites located in north-central France (FIG. 1). The total area reached ca. 15,000 ha. The sites were both typical of French intensive cultivated farmlands (see BRO et al., 2013) and of areas where wild populations of Grey Partridges still occur (BRO & CROSNIER, 2012). Spring pair densities varied from 5 to 60 pairs / km². Records of rain and temperature Precipitations (mm) and air temperature (°C) were recorded at hourly intervals from mid May to mid July with an automatic weather station (WS 23-55/57, La Cross Technology) on each study site. Sensor devices were fixed on stakes placed 1,50m above ground level in an open area so that data were comparable across study sites. Radiotracking survey Grey Partridges were surveyed in spring and summer 2010-2011 through radiotracking. Birds were captured at night from late February to late March, using a hand-held net and a light projector. Females were tagged and identified with a metal leg ring before being released. Handling time did not exceed a few minutes. Tags were necklace radio-transmitters including a 30-cm antenna (RI2DM, Holohil Ltd, Canada). They weighed 8g (so that the package was ca.2.5% of the body mass of lightest birds at the time of capture, see BRO et al., 1999), with a lifespan of 1 year and a reception range of ca. 1km in open landscapes. Tags were equipped with a motion-sensitive mortality circuit to discern survival. The mortality signal was emitted 2 hours after complete montionless of the radio-tag. A total of 437 partridge females were captured and monitored ≥ 7 days. The status (alive, dead or “missing”) of each radio-tagged bird was monitored twice a day since the day of its capture. Locations of birds were determined using triangulation and reported on a nomad GIS using a PDA-GPS

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2010

53

2011

≤3

≤4

]3-5]

]4-6]

]5-7]

]6-8]

>7

>8

FIG. 1.– Spatial variation in the breeding success (average number of offspring per female in summer, OFS) across the study sites in 2010 and 2011. Variation du succès reproducteur (nombre de jeunes par poule en été, OFS) entre les terrains d’étude en 2010 et 2011.

(JunoSB, Trimble). Incubation was detected when a female was located at the same place for consecutive days. Nest location was recorded using an averaged GPS measure. When an incubating female was located off its nest, hatching, clutch desertion or destruction was then suspected. Some additive locations were performed in the day before searching for the nest to confirm field appreciation. Clutch fate was identified to the appearance of eggs or eggshells. Hatching was identified by pipped eggshells. The presence of large holes in clean intact eggshells, or, less frequently, to large fragments of eggshells scattered around the nest, corresponded to predation. Compressed or crushed eggshells indicated a mechanical destruction, whereas intact pooled cold eggs indicated clutch desertion. The number of eggs laid was determined according to the number of eggshells and/or chorionic membranes. We considered it as a minimum number when the clutch had been destroyed. Eggshell of hatched or destroyed eggs were collected as well as intact eggs for further analyses (see below). A total of 301 clutches were monitored.

Brood survey Fields were searched by slowly driving a car along lanes and across fields at dawn and dusk when the birds were feeding in cereal stubbles or other patches of open grounds. When a covey was detected, we counted the number of cocks, hens and offspring using binoculars. The age of offspring was estimated according to their appearance (BIRKAN & JACOB, 1988). We sampled successful pairs as well as pairs without young (often groups of adults). A reliable estimate of breeding success was obtained by sampling at least 30-40% of pairs counted in spring on the same area (see BRO et al., 2005 for details on spring counts). Given that the spring to summer survival rate of breeding females ranged between 0.40 and 0.65 (see BRO et al., 2013), 50 to 80% of females still alive in summer were sampled. A total of 795 coveys were described, totalling 1151 males, 906 females and 5857 offspring. We estimated the breeding success both through the number of offspring per female in summer (OFS) and the proportion of females without offspring (FWO, corresponding to females

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Alauda 82 (1), 2014

whose clutch(es) failed as well as females that lost all their young). Both estimates are highly correlated with a high r².

been established on artificially incubated eggs from hand-reared partridges, for each day of development.

Embryological analyses The status (fertile vs. infertile) of each intact egg was determined by examining its content under a halogen illuminated stereomicroscope (10x, M27, Leica). Embryonic structures (embryonic disk) become visible after 2 days of incubation, thus the “infertile status” included both true infertility and early stages of embryonic mortality (≤ 2 days). When an embryo was observed, its stage of development was determined using reference standards (see BIRKAN & JACOB, 1988; BRO et al., 2013). Standards have

Relationship between clutch failure and rain We analysed the temporal coincidence between clutch failure, especially clutch desertion, and occurrence of rainy events. First we determined the incubation and laying periods for each clutch (back-calculation procedure using the date of hatching or failure as a starting point). A 24-day incubation was considered in case of hatching (BIRKAN & JACOB, 1988). In case of failure, when intact eggs with dead embryos were collected, we considered the age of the embryo with the older development stage as the

40 35

Temperature (°C)

June 15th

July 1st

A

30 25 20 15 10 5 hatching period

0 180 160 140 120 100 80 60 40 20 0

Amount of rain (mm) B

152

159

166

173

Day

180

187

194

FIG. 2.– Weather conditions from day 152 (June 1st) to 194 (July 15th) 2010. Daily temperature (A, Tmin: open symbols, Tmax: black symbols) and amount of rain (B). Average or sum values over the study areas (
) and data from two contrasted sites with either a low () or a high (∆) breeding success. Données climatiques du jour 152 (1er juin) à 194 (15 juillet) 2010. Température journalière (A, Tmin: symboles blancs, Tmax: symboles noirs, le trait noir horizontal indique la période d’éclosion des poussins) et pluviométrie quotidienne (B). Moyenne ou somme des terrains d’étude (
), et exemple de 2 terrains avec un succès reproducteur faible () ou élevé (∆).

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length of the incubation. The laying period was calculated as the number of eggs laid increased by a factor 1.5 which corresponds to the mean laying rate in Grey Partridges (BIRKAN & JACOB, 1988). Full or partial missing values corresponded to clutches for which all eggs were either “infertile” or rotten, or still to predated clutches for which only a few eggs were retrieved. On the other hand, we computed the date, the duration (hour) and the rain quantity (mm) for each continuous rainy event with a total ≥ 5mm of rain. The amount of rain was (arbitrarily) classified as follows: [5-10[, [10-15[, [15-20[, [20-30[, [30-40[, [40-50[, ≥50mm. For each rainy event, we calculated the proportion of clutches that failed the day D or D +1. Calculations were done sepTemperature (°C) 40

arately for the two stages “egg-laying” and “incubation” because the frequency and duration of female presence vary between these two periods, as well as egg protection (eggs are covered with vegetation during laying but not during incubation). Egg drowning and thus clutch desertion are likely to vary accordingly (BIRKAN & JACOB, 1988). Relationship between the breeding success and weather conditions Breeding success largely varied across study sites, both in 2010 and 2011 (FIG. 1). We examined the relationship between the local breeding success (OFS, FWO) and local weather conditions [daily minimum temperature (Tmin, °C), daily maximum temperature (Tmax, °C) and rainy July 1st

June 15th

A

35 30 25 20 15 10 5 hatching period

0 80 70

Amount of rain (mm) B

60 50 40 30 20 10 0 152

159

166

173 Day

180

187

194

FIG. 3.– Weather conditions from day 152 (June 1st) to 194 (July 15th) 2010. Daily temperature (A, Tmin: open symbols, Tmax: black symbols) and amount of rain (B). Average or sum values over the study areas (
) and data from two contrasted sites with either a low () or a high (∆) breeding success. Données climatiques du jour 152 (1er juin) à 194 (15 juillet) 2010. Température journalière (A, Tmin: symboles blancs, Tmax: symboles noirs, le trait noir horizontal indique la période d’éclosion des poussins) et pluviométrie quotidienne (B). Moyenne ou somme des terrains d’étude (
), et exemple de 2 terrains avec un succès reproducteur faible () ou élevé (∆).

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Alauda 82 (1), 2014 28 cases of clutch desertion according to field signs/information. Unfortunately 7 were attributed to field monitoring insofar desertion occurred within 1 day after clutch location. 8 cases were attributed to farming practices (harvesting), 4 to maintenance of landscape features (hedges, grassy banks) and 1 case to predation by corvids. We suspected stormy rains to have made incubating females desert their clutches in 1 case (see below). The cause of desertion was not identified for 7 cases.

events (amount (mm) and duration (hr))]. As a first step to dissect the data, we graphically examined the daily dataset to detect main patterns and contrasts across study sites (FIG. 2 & 3) to identify a priori biologically relevant mechanism (see Results section). We performed linear regressions using “lm” function (“stats” package, R).

RESULTS Fate of clutches monitored through radiotracking We determined with certainty clutch fate and cause of failure thanks to collected eggs/eggshells for 248 clutches. Globally, 50.8% of clutches hatched [2010: 50.9%; 2011: 50.7%]. 71.1% of clutch failure was due to the death of incubating females and/or to egg destruction [2010: 70.9%; 2011: 71.2%]. Clutch desertion accounted for 23.1% of clutch failure [2010: 23.6%; 2011: 22.7%], and lack of hatching despite and incubation time > 24 days for 3.3% [2010: 3.6%; 2011: 3%]. We attempted to determine the cause of the

Impact of heavy rains on clutch fate We recorded 97 events with at least 5mm of rainfall (whatever the duration). For each individual event (on a given site at a given time), 0 to 7 clutches were monitored at the egg-laying stage, and 0 to 9 at the incubation stage. Only few cases of clutch failure were observed in coincidence with stormy rains (TAB. I). All but one were attributed to predation (death of the incubating female and/or destruction of eggs). Only one case was attributed to a stormy rain on the basis of clutch desertion during hatching. No desertion case was associated with ≥ 15mm or even

TABLE I.– Numbers of monitored clutches at the egg-laying or incubation stages, number of clutches that failed at day D or D+1 coinciding with different rainy regimes. Nombre de pontes suivies aux stades « ponte » et « couvaison », nombre de pontes ayant échoué (dont par abandon) le jour J ou J+1 par rapport à différents régimes de pluie décrits par leur durée (en heures) et la quantité d’eau tombée (en mm). NUMBER OF CLUTCHES

NUMBER OF CASES OF:

Egg-laying stage

Incubation stage

Failure

Desertion

Number of events

[30-40[ [20-30[ [15-20[ [10-15[ [5-10[

0 15 1 15 44

2 28 6 14 92

0 0 0 3 4

0 0 0 1 1

1 8 3 9 37

2 2 2 2 2

>50 [30-40[ [20-30[ [15-20[ [10-15[

0 0 2 0 14

2 1 7 2 31

0 0 0 1 3

0 0 0 1 1

1 1 3 3 10

3 3 3 3

> 50 [20-30[ [15-20[ [10-15[

0 1 0 2

2 0 4 1

0 0 1 0

0 0 1 0

1 1 1 1

Duration (hour)

Quantity (mm)

1 1 1 1 1

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Cumulated %

June 1st

57

July 1st

August 1st

100 80 60

40 Hatching 2010 (N = 64) Hatching 2011 (N = 77) Failure 2010 (N = 74) Failure 2011 (N = 82)

20 0

122 129 136 143 150 157 164 171 178 185 192 199 206 213 220 227 234 241 Day

FIG. 4.– Cumulated % of hatched and failed clutches in 2010 and 2011. Pourcentage cumulé d’éclosion (symboles blancs) et d’échec (symboles noirs) des pontes en 2010 (cercles) et 2011 (triangles).

[20-30[ mm of rain fallen in one hour, which is quite violent and exceptional in central-northern France. The heaviest rain (a total of 64.7mm of rain fallen in 6 hr) was recorded on the site at the western of Paris July 14th 2010. All the monitored clutches but two had hatched or failed at this date. The last two ones failed 10 and 18 days later. Both were probably incubated but unfortunately this could not be established with certainty because we could not determine the age of dead embryos. In one case, the 14 eggs were found rotten, being incubated for more than 40 days according to radiotracking data. In the other case, both the female and her 10 eggs have been destroyed by a mowing machine. In addition, we monitored some tagged females that did not desert their clutch despite repeated heavy rains within few days. For example, 7 over 9 hens successfully incubated their clutch despite a first heavy rain (25mm in one hour) at day D and an other rainy event two days later (49.8mm in 10 hours, with peaks of rainfalls of 23.9, 9.8 and 5.7mm fallen in one hour). However, we observed a high rate of clutch failure June 10th 2010 (day 161) when heavy rains

occurred on most sites (FIG. 4 & 2B). The cases of clutch desertion that was attributed to rainfalls corresponded to these events. This could be a plausible cause for a few further cases but it could not be confirmed because the corresponding clutches have not been retrieved. We did not observe the same July 14th (day 195) both because stormy rains only fell on a few sites, and occurred after most clutches have already hatched or failed (FIG. 4 & 2B). Breeding success and rain At the national scale, June and July 2010 were dry with occurrence of rainy storms (METEO FRANCE, 2011). This pattern was similar in June 2011 but July 2011 was the wettest since 1959 (METEOFRANCE, 2012). This historically high record of rain has both resulted from a rainy weather together with stormy rains. The differences in the breeding success observed in 2011 across study sites were negatively correlated with the total amount of rain fallen early July and the number of rainy days. Best fits were observed with FWO (amount of rain: F1,7 = 23.6 ; P = 0.002 R²adj = 0.738 ; number of rainy days:

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Alauda 82 (1), 2014 % female without offspring

A

50

B

50

40

40

30

30

20

20

10

10 0

0 0

2

4

6

8

10

12

14

0

16

Amount of rain July 1st - 7th (mm)

1

2

3

4

5

6

Number of rainy days July 1st - 7th

FIG. 5.– Relationships between the proportion of females without offspring and (A) the amount of rain fallen early July and (B) the number of rainy days. Corrélations entre la proportion de poules sans jeunes et (A) la pluviométrie totale et (B) le nombre de jours de pluie du 1er au 7 juillet.

F1,7 = 20.2 ; P = 0.003 ; R²adj = 0.705, FIG. 5). The two sites showing the lowest breeding success experienced more or less continuous rains associated with cooler temperatures (average Tmax over July 1st- 7th of 22.9°C in contrast to 29.4°C on sites with only one rainy day) - but minimum temperatures were a bit milder on those two sites (11.3 vs. 9.2°C). Both were located near the Channel. Breeding success and temperature Early summer 2010 was warm in north-central France (FIG. 2A ; METEOFRANCE, 2011). However, a “cold spell” with minimum temperatures as low as 5-7°C occurred June 20th, coinciding with chick hatching. If it only lasted a few days (June 20-21/24th) on some study sites, it extended until early July (July 4-7th) on other sites (FIG. 2A). Except for an outlier, the difference of breeding success across study sites was correlated to the difference in the average Tmin during this period (F1,6 = 7.49 ; P = 0.034 ; R²adj = 0.481, FIG. 6). No correlation was detected with maximum temperature, Tmax being more homogeneous across study sites (FIG. 3A). In 2011, if spring and early summer were warm, July was recorded as the coolest July since 1981 (METEOFRANCE 2012). Minimum temperature

Offspring / female in summer 10

8

6

4

2

0 7

9

11

13

15

Average Tmin (° C) June 20th - July 7th, 2010

FIG. 6.– Relationship between the breeding success and the minimum daily temperature averaged for June 20th - July 7th period. The grey point represents an outlier. Corrélation entre le succès reproducteur et la température journalière minimale moyennée du 20 juin au 7 juillet. Le point gris représente une observation « marginale ».

17

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Impact of climate on Partridge reproduction decreased the June 10-12th (just before chick hatching), June 17th & 24th and July 2-4th (FIG. 3A). By contrast with 2010, these events were short (one or two days) and more or less occurred on all sites. No significant relationship with the breeding success was detected.

DISCUSSION Weather conditions have been reported to strongly influence Grey Partridge breeding success (REITZ, 1988; see reviews by BIRKAN & JACOB, 1988 and POTTS, 2012). In the present study, we did not detect any clear effect of heavy rains on clutch failure, in particular clutch desertion. However, the marked spatial differences in breeding success across the study sites were correlated to the occurrence of a 2-week cold spell during the hatching period in 2010, and to moderate rainfalls coupled with relatively fresh temperatures in 2011. Heavy rains may have direct effects on clutch and chick survival rates. Eggs may be drowned by heavy rains, especially on clay soils (e.g. BIRKAN, 1977; AUBINEAU, 1981). Laying and incubating females may also desert their nests when such rains and/or strong winds induce lodging in the crop cover where clutches are laid. This is often observed in cereal crops, the preferred nesting cover in French cereal ecosystem (BRO et al., 2000b, 2013), in spite of the use of growth regulators. Such mechanism was explicitly reported during our 1995-1997 radiotracking study (see BRO et al., 2000c). In the present study, ca. 1% of clutch failures was attributed to weather events (this proportion accounted for 5.5% in 19951997, BRO et al., 2000c, 2013). FANT (J. Anim. Ecol., 1953 in BIRKAN & JACOB, 1988) recorded the movements of incubating females. He showed that partridge females frequently leave their nests but shortly in case of inclement weather, and that they barely move on their nests in case of heavy rains. This behaviour may explain why the stormy heavy rains we regularly experience in central-northern France do not systematically lead to clutch desertion as it is usually believed (see discussion in BRO et al., 2009). Unfortunately, we could not really assess the impact of ex-

59 ceptional heavy rains (total of 64.7mm within 6 hours - with 39.4mm in 1 hour and 51.3mm in 2 hours) that occurred in mid-July 2010 on clutch desertion because most clutches had hatched or failed at this time. Such rainfalls are suspected to have much more adverse effects, as reported by AUBINEAU (1981) and as suggested by crop irrigation (BIRKAN et al., 1990). It is all the more a shame that they are currently not so common local events (see http://pluiesextremes.meteo.fr) but they are likely to become more frequent in a near future (e.g. GIEC, 2007; LARSEN et al., 2008; MITCHELL & VAN AALST, 2011). Early summer rainfalls strongly influence the timing of crop harvest. The Grey Partridge nests in a variety of crop cover among which the winter wheat and the winter barley are the preferred ones (BRO et al., 2000b, 2013). Winter barley may be harvested as soon as late June depending upon regions, winter wheat in July (see FIG. 7). If farming practices are only marginally responsible of female mortality during spring and summer, they represent ca. 20% of clutch failure (N = 97; BRO et al., 2013). Replacement clutches generally suffer more from farming destruction (36%, N = 42) than first clutches (9%, N = 55) because hatching period of replacement clutches coincides with cereal harvesting (see figures 4 & 7). This was not the case a few decades ago, cereal crops were harvested in August (e.g. early August in the Beauce region in 1977 and mid- to late August in the Soissonnais region; AUBINEAU 1981). Thus clutches benefit from thin rains that delay cereal harvesting. This was clearly observed in 2010. Due to an unusual warm period at springtime, vegetation has grown nearly 2-3 weeks earlier than normal. In the example presented in figure 7, the rains that occurred just after midJune delayed harvesting of winter barley for ca. one week. This was likely to be beneficial to chicks that mostly hatched the second half of June. A rain of 21mm (in 3 hours) July 3rd also stopped harvesting rate, as well as those that occurred between the 9th and July 14th. This was also likely to be beneficial to chicks that do not fly until they are a few weeks old, and thus are proned to be destroyed by combines. When rains stopped and after grains were dry enough, cereal fields were harvested at a high rate.

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June 15th

July 1st

spring barley

Rain (mm) 30

July 15th

winter wheat

100

Rain winter barley

Harvesting

90

25

70

hatching

20

60 15

50 40

10

30 20

5

% harvested area of cereals

80

10 0

0 152

156

160

164

168

172

176

180 184 Day

188

192

196

200

204

208

212

FIG. 7.– Chronology of harvesting of cereal crops (winter barley, winter wheat and spring barley; 80 fields, 248ha) and occurrence of rains from June 1st to July 31st, 2010. Study site located near Blois. Pourcentage cumulé (G) de la surface en céréales moissonnée au cours des mois de juin et juillet (par ordre: orge d’hiver, blé d’hiver et orge de printemps; 80 parcelles totalisant 248ha) et occurrence de pluies du 1er juin au 31 juillet 2010 (barres grises). Le trait noir horizontal indique la période des éclosions. Site d’étude près de Blois (Loir-et-Cher).

Low temperature is also known to increase chick mortality, especially when insect food is limited. Dry and warm weather conditions as well as food abundance and diversity are important factors for chick survival until they reach 23 weeks old. Indeed, they quasi exclusively feed on invertebrates and they do not thermoregulate yet during this period (e.g. BORG & TOFT, 2000; BRO & PONCE-BOUTIN, 2004; SOUTHWOOD & CROSS, 2002 and references therein). Therefore the extended cold spell that occurred late June – early July 2010 is a biologically relevant hypothesis to explain the low breeding success observed on some study sites. Weather conditions have also indirect effects on chick survival both through insect food resources (that are favoured by wet and warm weather events) and chick foraging activity (that is reduced during periods of

low temperature, rain or dew; GREEN, 1984). As a conclusion, during the two years of the field study, some contrasted weather events had a direct effect on the Grey Partridge breeding success. This effect was strong enough to be clearly detected. It confirms the importance of this ecological factor in population dynamics, and the suspected importance of the global climatic change. Although changes will not be manageable per se, research should be planned to investigate their short and long term effects and, if relevant, to reappraise management strategies (see REITZ, 2003) to ensure long term exploitation and conservation. The field data presented in this paper may be useful to parameterize ecological relationships within a demographic model. Such tool will serve to examine the projections of different climatic scenarios.

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Impact of climate on Partridge reproduction ACKNOWLEDGEMENTS

This study is part of the PeGASE study conducted by the National Game & Wildlife Agency (ONCFS) and several hunter associations (FDC 14, 27, 28, 41, 45, 51, 59, 62, 76, 77, 80, Fidif and FRC-CA). It was funded by participants and Europe (FEDER), France (FNADT, CG 27, 41 & 76), hunter associations (FNC, MCN, CEB, SCIF) and other associations (ASP Limousin, Vermillon). The work was conducted in association with field technicians of hunter associations. We acknowledge the landowners and the hunters for giving us permission to work on their land. The daily standard of embryonic development in the Grey Partridge was realized by A. MESBAH (ONCFS - Fertil’avi - University of Tours). A. MESBAH was advised by J.-P. BRILLARD (Fertil’avi) and C. BRESSAC (University of Tours). Embryological analyses were performed by A. MESBAH, J.-P. BRILLARD and E. BRO (ONCFS). F. REITZ (ONCFS) and C. BRESSAC (University of Tours) provided helpful comments when writing the ms. This study was conducted in accordance with the principles and specific guidelines of the French legislation for animal welfare and wildlife regulations. A prefectoral bylaw authorised the researchers and their associates to collect, transport and have these eggs during the study years (arrêté n° 2010-013, Préfecture de Paris).

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