Read Relazione tordo 41-07 Arosio text version

FONDAZIONE EUROPEA IL NIBBIO

POST-NUPTIAL MIGRATION OF SONG THRUSH (Turdus philomelos):

DATA COLLECTED for 68 YEARS (1941-2008) at the AROSIO BIRD OBSERVATORY (COMO, ITALY)

OSSERVATORIO ORNITOLOGICO FEIN via Cascina Perego n. 1, 22060 Arosio (CO) Tel/Fax 031-762162 E-mail [email protected] Web Site www.nibbio.org

by Silvia Capasso in collaboration with Paola Magnani

The Fondazione Europea Il Nibbio (FEIN) ­ Onlus (Foundation for bird migration research and environmental protection) has been founded in 1988 in order to contribute to the conservation of the fauna and the natural habitats. The FEIN manages the Ornithological Observatory of Arosio, Como, in Lombardy (Northern Italy, 45°43'N ­ 09°12'E) which, since 1977, has been carrying out a standardized scientific bird ringing activity that has allowed to ring over 162.000 birds. The vegetation consists of small shrubs and corridors of Hornbeam (Carpinus betulus), while the neighbouring wood is made up of Sweet Chestnut (Castanea sativa) and Black Locust (Robinia pseudoacacia). A lot of data referring to the period before 1977 are available at Arosio; the Observatory, in fact, has developed from the transformation of an ancient Roccolo (a typical facility of Lombardy, used to catch birds), dating back to 1710; hunting with nets has been used until 1957. From 1958 to 1976 there was a ringing activity, not yet controlled or coordinated, but a constant and standardized scientific ringing activity started in 1977. From 1941 to 2008, for 68 years, the capture activity has been continuous and constant (except in 1969), in particular during the autumnal migration the station, equipped with about 700 meters of mist-nets, has been always active from 4 August to 31 December. Therefore, it is possible to show for the Song Thrush (Turdus philomelos), one of the most ringed species, a short analysis of the data collected in the period 1941-2008.

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The Song Thrush, a polytypic and Eurosibiric species, is uniformly distributed as a breeder in all wooded areas of Central and Northern Europe, Western Siberia and Asia, whereas in Southern Europe it is particularly present on mountains. This bird is a short/medium distance migrant, characterized by populations which are partially or completely migratory. It winters in the CenterSouthern areas of Europe and in the Mediterranean region. In Lombardy it is a regular migrant, partially wintering, which constantly breeds across the Alps and in the hilly region of the Pavian Apennine, at an altitude of 250-1900m, sometimes coming up to 2000m (Brichetti & Fracasso, 2008).

In Italy and many other European countries, first of all France, Spain and Greece, the Song Thrush is subject to a

strong hunting pressure. This species is included in Appendix III of the Berne Convention and Annex II/2 of the "Birds the Directive" 79/409/EEC,

IUCN Red List of Threatened Species classifies it as "Least Concern" (LC) and BirdLife International classifies it as "Non-SPECE ".

In the period 1941-2008 at the Arosio Bird Observatory 50.345 Song Thrushes have been catched, most of them during the post-nuptial migration. As shown by the diagram (Figure 1), the year with the highest number of captures was 2008 (1.758 birds); the year 1943 follows with 1.684 Song-Thrushes captures. During the autumns of the last two years, 2007 and 2008, Arosio and many localities of northern and central Italy have registered a very intense migratory passage for many species. Confronting the data concerning the three different stages that the Observatory has going through (hunting, not coordinated ringing activity, coordinated scientific ringing activity) there are not significant differences and the captures show a rather continuous trend; the little fluctuations recorded in some years belong to the normal trend of the avian migration phenology, because large variations in the passages of migrants can happen from year to year.

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1758 1040

768 974 694 1025

634 732 644

459 426 734

838 852 604

355 684 550 650 672

887 823 868

669

806 801 627 605

527 590 580

740

505 568 590 878

634 721 753 675

505 544 1097

628 696

920 548 899 594

704 722 778

902 1017 1491 1163

1684 1182 1041

Figure 1: Number of captures for year, 1941-2008.

900

800

700

600

500

400

300

200

1900

1800

1700

1600

1500

1400

1300

1200

1100

Number of captures

1000

100

0

Year

592 642 521 525 600 464 535 411

2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 1993 1992 1991 1990 1989 1988 1987 1986 1985 1984 1983 1982 1981 1980 1979 1978 1977 1976 1975 1974 1973 1972 1971 1970 no activity 1968 1967 1966 1965 1964 1963 1962 1961 1960 1959 1958 1957 1956 1955 1954 1953 1952 1951 1950 1949 1948 1947 1946 1945 1944 1943 1942 1941

Total number = 50.345

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Table 1 represents the days of maximum captures and the respective number of Song Thrushes, from year to year; the trend of the peaks in the course of the 68 years is visible in the diagram of Figure 2. In four years only (1958, 1977, 1993 and 2008) the maximum capture day was in September. The latest peak date in autumn was the 21st October (years 1980 and 1982), while the 10th of October is the day in which the maximum number of captures has been recorded more times (for 9 years). From the diagram it appears an interesting cyclical trend of the peak days. In fact, we can see four cycles in which "late" peak days (after the 1st half of October) or "early" peak days (end of September-beginning of October) are repeated every 15-18 years approximately.

YEAR

MAXIMUM CAPTURE DAY

NUMBER of CAPTURES

YEAR

MAXIMUM CAPTURE DAY

NUMBER of CAPTURES

YEAR

MAXIMUM CAPTURE DAY

NUMBER of CAPTURES

2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 1993 1992 1991 1990 1989 1988 1987 1986

28/09 2/10 11/10 6/10 14/10 14/10 01/10 10/10 18/10 14/10 16/10 14/10 12/10 11/10 07/10 30/9 11/10 05/10 06/10 05/10 9/10 02/10 11/10

132 96 85 136 101 151 53 50 51 54 34 59 72 61 43 42 59 71 58 49 91 132 72

1985 1984 1983 1982 1981 1980 1979 1978 1977 1976 1975 1974 1973 1972 1971 1970 1969 1968 1967 1966 1965 1964 1963

18/10 17/10 14/10 21/10 08/10 21/10 08/10 09/10 28/09 10/10 09/10 06/10 04/10 04/10 04/10 12/10

No activity

46 52 38 42 40 36 34 52 62 78 71 53 104 44 39 54 71 49 52 81 85 76

6/10 15/10 06/10 10/10 03/10 10/10

1962 1961 1960 1959 1958 1957 1956 1955 1954 1953 1952 1951 1950 1949 1948 1947 1946 1945 1944 1943 1942 1941

04/10 03/10 03/10 07/10 30/9 10/10 12/10 04/10 10/10 10/10 10/10 06/10 15/10 09/10 11/10 12/10 10/10 09/10 08/10 11/10 08/10 03/10

60 65 71 71 48 178 86 62 184 108 120 62 182 108 85 102 167 173 127 277 120 102

Table 1: Day of maximum capture and respective number of Song Thrushes, 1941-2008. (Bold type: more than 100 captures; red type: peaks in September)

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Figure 2: Days of maximum capture, 1941-2008. For the last 16 years (1993-2008), for which a computerised archive is available, it has been possible to calculate the age-ratio of the birds during the post-nuptial migration (period 1 September ­ 20 November). The sample is composed of 9.790 juveniles, 2.315 adults and 118 undetermined (total = 12.223). The young/adult is therefore equal to 4.2, while the percentage of young birds is equal to 81%. Similar analysis, carried out for birds ringed in autumn in the Alps, below the 700 m a.s.l., (Pedrini et al., 2008) and in Campania (Scebba, 2006), revealed slightly higher percentages of juveniles, respectively equal to 86% (period 1997-2002) and 83% (period 2003-2005).

Wing of a young bird: presence of juvenile great coverts

(according to Svensson, 1992)

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At last, Table 2 represents a synthesis of the numerous recoveries (more than 300) of Song Thrushes ringed in Arosio and recaptured elsewhere (period 1977-2008); the collected data allow to locate in France, Algeria, Spain and Corsica the main destinations for the wintering, and to confirm for Italy a pre-eminent migratory flyway towards the south-west, through the Piemonte and Liguria Italian regions, with a branch flyway towards the South, through Tuscany and Lazio (see figure on the right). Besides, it is important to explain that a foreign recovery has been recorded during 2008 at the Observatory: a Song Thrush with a ring (H79387) of the ringing center of Sempach (Switzerland). Further information is to come from the Italian ringing center (ISPRA, ex INFS, Ozzano dell'Emilia-BO).

RECOVERY PLACE NUMBER of RECOVERIES RECOVERY PLACE NUMBER of RECOVERIES RECOVERY PLACE NUMBER of RECOVERIES RECOVERY PLACE NUMBER of RECOVERIES

FRANCE ALGERIA SPAIN BALEARI CORSICA

80 GERMANY 50 GREECE 23 LETTONIA 21 CZECH REPUBLIC 11 ITALY - LOMBARDY

1 ITALY - LIGURIA 1 ITALY - TUSCANY 1 ITALY - LAZIO 1 ITALY - VENETO 79 ITALY - PIEMONTE

15 ITALY ­ SARDINIA 9 ITALY - UMBRIA 4 ITALY - CAMPANIA 4 ITALY - CALABRIA 3

2 1 1 1

Table 2: Recoveries of Song Thrushes, ringed in Arosio and recaptured elsewhere (1977-2008).

References

Brichetti P. & Fracasso G., 2008. Ornitologia italiana. Vol. 5 Turdidae-Cisticolidae. Oasi Alberto Perdisa Editore, Bologna. Pedrini P., Rossi F., Rizzolli F., Spina F., 2008. Le Alpi italiane quale barriera ecologica nel corso della migrazione post-riproduttiva attraverso l'Europa: risultati generali della prima fase del Progetto Alpi (1997-2002). Biol. Cons. Fauna 116: 183-184. Scebba, 2006. Tordo bottaccio Turdus philomelos: studio della migrazione autunnale in Campania. Gli Uccelli d'Italia XXXI: 26-49. Svensson L., 1992. Identification guide to European passerines. Stockholm.

Song Thrush with a swiss ring, captured in Arosio on 7 October 2008

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Relazione tordo 41-07 Arosio

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