Changes in the timing and pattern of arrival of the White Stork
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
J. Ornithol. 144, 323±329 (2003)
ã Deutsche Ornithologen-Gesellschaft/Blackwell Verlag, Berlin
ISSN 0021-8375
Changes in the timing and pattern of arrival of the White Stork
(Ciconia ciconia) in western Poland
J. Ptaszyk1, J. Kosicki1, T. H. Sparks2 and P. Tryjanowski1 *
1
Department of Avian Biology & Ecology, Fredry 10, PL-61±701 PoznanÂ, Poland; (*corresponding author;
Email: ptasiek@main.amu.edu.pl)
2
Centre for Ecology and Hydrology, Monks Wood, Abbots Ripton, Huntingdon,
Cambridgeshire PE28 2LS, UK
Summary
Changes in the spring arrival dates of migrant birds, particularly passerines, have been
reported from a range of locations. In this paper we take the opportunity provided by a
detailed monitoring scheme to examine several features of the timing and arrival pattern of
White Storks (Ciconia ciconia) in Poznan province, western Poland during the period
1983±2002. In doing so, we address several criticisms associated with the use of first
arrival dates. We found no evidence of a weekend bias to phenological recording and, un-
like in some other species, found no effect of population size on recorded arrival date.
Some aspects of the arrival pattern got earlier over time and first arrival appears to have
been about 10 days earlier in the last 20 years than in the previous century. Earlier arrival
was associated with warmer spring weather and with a protracted arrival period. From our
experience with this study, we suggest how the general public can be used to collect high
quality phenological data.
Keywords: phenology, birds, population size, migration, methods.
Zusammenfassung
È nderungen im Ankunftsmuster beim Weiûstorch (Ciconia ciconia) in Westpolen
A
AÈ nderungen im Zeitpunkt der FruÈhjahrsankunft bei ZugvoÈgeln, vor allem bei SingvoÈgeln,
wurden von verschiedenen Orten berichtet. In dieser Arbeit nutzen wir die MoÈglichkeiten
eines detaillierten Monitoring-Programmes, um die verschiedenen Merkmale des An-
kunftsmusters des Weiûstorchs (Ciconia ciconia) in der Provinz Posen (PoznanÂ, Westpo-
len) im Zeitraum 1983±2002 zu untersuchen. Wir betrachten hierbei vier Aspekte: 1) Gibt
es einen Wochenend-Effekt in den erhobenen Daten? 2) Beeinflusst die PopulationsgroÈûe
den festgestellten Ankunftszeitpunkt? 3) Gab es uÈber die Jahre A È nderungen in den An-
È
kunftszeiten? und 4) welche Ursachen liegen den Anderungen in Ankunftszeiten zu Grun-
de? In diesem Zusammenhang formulieren wir einige Kritikpunkte zur Verwendung von
Erstankunftsdaten. Wir fanden keinen Hinweis auf einen Wochenend-Effekt auf die phaÈ-
nologische Datenerfassung und, im Gegensatz zur Situation bei einigen anderen Arten,
keinen Effekt der PopulationsgroÈûe auf das registrierte Ankunftsdatum. Einige Merkmale
des Ankunftsmusters verfruÈhten sich im Laufe der Zeit und die Erstankunft liegt nach 20
Jahren offenbar uÈber 10 Tage fruÈher als im vorigen Jahrhundert. FruÈhere Ankunft stand in
U.S. Copyright Clearance Center Code Statement: 0021-8375/2003/14403±0323 $ 15.00/0324 Journal fuÈr Ornithologie 144, 2003
Verbindung mit waÈrmerem FruÈhlingswetter und mit einer verlaÈngerten Ankunftsphase.
È ffent-
Aus unseren Erfahrungen mit dieser Untersuchung schlagen wir vor, wie die breite O
lichkeit zur Sammlung hochqualitativer phaÈnologischer Daten genutzt werden kann.
Introduction rival data and can test the relationships be-
tween different measures of arrival time.
The dates when migrant birds return to their Berthold (1991) hypothesised that global cli-
breeding areas are often used for measuring mate change could be dangerous to the White
the impact of climate change on bird popu- Stork population, mainly through increased
lations (Berthold 1991, Sparks 1999, Tryja- changes to habitats, e.g. drainage. In this con-
nowski et al. 2002). However, many analyses text, we also check changes in arrival dates
do not consider the possible problems associa- during the study period, and make compari-
ted with population size effects or biases from sons with older data collected across Europe
weekend recording. The former could affect (Sliwinsky 1938, Zabøocka 1959, Beklova
the detection of bird arrival time through (1) et al. 1983, Ptaszyk 1994, Zalakevicius &
higher probability of observing earlier arrival Zalakeviciute 2001).
when population size is bigger, and (2) increa-
In this paper we consider four aspects of the
sed social activity e.g. aggression, relative to
timing and arrival pattern of White Stork in
population size and hence earlier observation.
western Poland: 1) Is there a weekend bias in
the recorded data (Fraser 1997; Sparks 1999)?
So far, information on population size ef-
2) Does population size influence recorded
fects on recorded arrival time is limited to
arrival date? 3) Have there been changes in
cryptic birds, which are not easy to detect in
arrival dates over the years? and 4) What are
the field, such as the Red-backed Shrike
the causes behind any changes in arrival dates?
(Lanius collurio; Tryjanowski & Sparks
2001). In contrast, the White Stork (Ciconia
ciconia) is a large, conspicuous, soaring mi- Materials and Methods
grant with very obvious roosts and nest sites. It
is well known to the general public, and in The study was conducted during 1983±2002, in the
Central European countries is a traditional agricultural landscape of western Poland, near Poz-
ªsign of springº (Lewandowski & Radkiewicz nan (52° N, 16°E) this area of 1483 km2 arable fields
1991). It breeds in parts of Europe, the Middle are interspersed with meadows, pastures, human
East and North Africa, and the Central Euro- settlements and small woods (for details see Ptaszyk
1994a). In the study area the White Stork nests
pean population winters in tropical Africa
mainly on roofs of farm buildings, electricity pylons
(Schulz 1998, Berthold et al. 2001).
and trees which makes the nests extremely conspi-
cuous; they are also used year after year.
Arrival can be measured not only by first re-
Arrival dates of White Storks on the nests were
corded arrival dates (FAD), as used in many
recorded on special forms by farmers living near
phenological studies, but also by more general occupied nests and sent direct to the authors. The
population characteristics, eg. median arrival return rate of the record sheets varied annually from
date, arrival date of the third individual (TAD) 71±85 % (mean ± SD 78 ± 5 %).
(Sparks et al. 2001). Sparks (1999) concluded
The population size and productivity of the local
that the relationship between first arrival dates population were established by standard methods
and the bulk movement of the population nee- used during the International Census of White
ded investigation to establish the value of first Storks (Creutz 1985, Schulz 1998). In each year
dates in phenology. Fortunately, for the White FAD, TAD and median date were determined and
Stork we have good quality population and ar- the range of dates (last minus first dates) calculated.J. Ptaszyk et al. ´ Arrival of White Stork in Poland 325
Monthly air temperature data for the period
1983±2002 were obtained from the Poznan me-
teorological station.
All basic statistical analyses were applied accor-
ding to the recommendations of Sokal and Rohlf
(1995) and were conducted using the statistical
package SPSS/PC+ (Norusis 1994).
Results
Weekend bias
Fig. 1. Frequency distribution of the weekdays of
The distribution of observations between the first arrival date.
days of the week did not differ significantly Abb. 1. HaÈufigkeitsverteilung der Wochentage
from a random pattern (c2 = 2.32, df = 6, p = von Erstankunftsdaten.
0.88), so did not indicate a weekend bias
(Fig. 1).
ranged from 2nd April to 23rd April, with a
The influence of population size median of 6th April. The different measures
on arrival time of White Stork arrival time were positively
correlated; FAD was strongly correlated with
The number of breeding White Stork pairs in TAD (r = 0.79, p < 0.001) and TAD was signi-
the study area varied between 51 and 76 (mean ficantly correlated with median date (r = 0.69,
± SD 64.9 ± 8.5) and increased significantly p < 0.001). However, FAD was only weakly
during the 20-year study by about a pair a year correlated with median arrival date (r = 0.38,
(slope = 1.054, r2 = 53.9 %, p < 0.001). The p = 0.099).
mean density of breeding pairs thus varied
During the period 1983±2002 the FAD
from 3.5 to 5.2 (mean ± SD 4.5 ± 0.6) per
(slope ±0.55 ± 0.21, p = 0.017) and TAD (slope
100 km2.
±0.51 ± 0.21, p = 0.032) became significantly
Contrary to expectation, we did not find a earlier (Fig. 2) but median arrival date did not
significant negative correlation between (slope ±0.08 ± 0.19, p = 0.67). Extensive data
arrival date measures and population size (r = on the arrival time of this species are available
±0.19, ±0.30, ±0.30 for FAD, TAD and median from the end of the 19th century. Sliwinsky
date respectively, p > 0.19 in all cases). Even (1938) reported that the mean arrival date of
after the elimination of any linear trend the White Stork in the Wielkopolska region in
through time, by the use of multiple regressi- the 1930s was between 30th March and 4th
on, the partial effect of population on all three April and was similar to dates at the end of the
arrival date measures was not significant (p > 19th century. In the 1950s storks arrived on
0.15 in all cases). The range of recorded dates average on 1st April (Zabøocka 1959). This
was not related to population size (r = 0.08, p = suggests that the first White Stork now returns
0.75). from the wintering grounds ca. 10 days earlier
than it did 100 years ago.
Changes in arrival time patterns
Years with earlier FAD were associated
In the study area FAD of the White Stork va- with a wider range of arrival dates (Fig 3A,
ried between the 11th March and 1st April r = ±0.77, p < 0.001). In a further examination
(median 23rd March). The third bird (TAD) of this aspect, the symmetry of arrival was cal-
varied between 19th March and 5th April (me- culated as the difference between last and me-
dian 29th March) and median date of arrival dian dates divided by the difference between326 Journal fuÈr Ornithologie 144, 2003
median and first dates; a value of one suggests
symmetry whilst large values suggest a skew
towards later dates. There is a positive rela-
tionship between FAD and this measure of
symmetry (Fig. 3B, r = 0.53, p = 0.016) sug-
gesting that later FADs, particularly after 21st
March (day 80), are associated with more skew
arrival distributions.
Influence of temperature on arrival
Fig. 2. Arrival dates (days after 31st December) FAD was marginally related to February±
of the White Stork in the study area. Median dates March mean local temperature (slope ±0.55 ±
are indicated by a solid symbol, third arrival dates 0.27, p = 0.053) and TAD was significantly re-
by an open circle and first arrival dates appear with- lated to this temperature measure (slope ±0.62
out a symbol. Distance weighted smoothed lines ± 0.27, p = 0.030). However, there was no rela-
(LOWESS) are superimposed as solid lines.
tionship between median date and temperature
Abb. 2. Ankunftsdaten (Tage nach dem 31. De-
zember) des Weiûstorchs im Untersuchungsgebiet. (Figure 4; slope ±0.07 ± 0.23, p = 0.75).
Mediandaten sind durch ein ausgefuÈlltes Symbol
gekennzeichnet, Daten der Ankunft des dritten Vo-
gels durch einen Kreis und Erstankunftsdaten sind Discussion
ohne Symbol dargestellt. Nach Distanz gewichtete
GlaÈttungslinien sind als durchgezogene Linien The White Stork is large, conspicuous, easily
(LOWESS) daruÈber gelegt. recognised and is acknowledged by the general
Fig. 3. The relationship of first arrival date with A) the range of arrival dates and B) the symmetry of
arrival (see text for details).
Abb. 3. VerhaÈltnis zwischen Erstankunftsdatum und A) Zeitspanne der Ankunftsdaten und B) Symmetrie
des Ankunftsmusters. Details siehe Text.J. Ptaszyk et al. ´ Arrival of White Stork in Poland 327
tures for periods of up to 4 weeks (Mata et al.
2001). Therefore temperature is unlikely to im-
pact directly on the stork, but rather via modu-
lation of their food supply (Hughes 2000). An
examination of changes to temperatures along
migration routes merits further investigation.
Sparks (1999) and Tryjanowski & Sparks
(2001) suggested a need to investigate the rela-
tionship between first arrival date and popula-
tion size, and identified a problem with Turtle
Dove (Streptopelia turtur) and the Red-backed
Fig. 4. The relationship between first (+), third (o) Shrike. Additionally Sparks et al. (2001) pro-
and median (·) arrival dates and February-March duced a theoretical model suggesting a strong
mean temperature. Regression lines have been relationship between first arrival detection
superimposed.
date and population size. However, this poten-
Abb. 4. VerhaÈltnis zwischen Ankunft des ersten
(+) und des dritten (o) Vogels bzw. Lage des An- tial problem is rarely acknowledged in other
kunftsmedians (·) zu den Temperaturmittelwerten phenological papers. One reason for this may
Februar±MaÈrz. Regressionsgeraden wurden daruÈber be the lack of contemporary data on both
gelegt. arrival and population size. Our results ob-
tained for White Storks are in conflict with
previous results and suggestions. This is
public as a harbinger of spring (sensu Sparks probably due to the effect of several factors;
1999). Its arrives in Europe much earlier than populations are relatively stable year-to-year,
other long distance migrants, especially passe- birds are large, obvious and associated with
rines, that breed in Central and Eastern Europe human habitation and they return to the same
and winter in tropical Africa (Berthold 1991, nest sites each year. For these various reasons,
Tryjanowski et al. 2002). Like some other spe- our findings for White Storks may not be ap-
cies the White Stork has changed aspects of its plicable to other species. The tendency for
arrival time during the study period (Tryja- White Stork aggressive behaviour to increase
nowski et al. 2002). Considered over a longer with population size (SchuÈz 1944, Profus
time period the White Stork in Poznan provin- 1986, Schulz 1998) did not seem to influence
ce has tended to become markedly earlier. its appearance.
A change in migration behaviour is also be- We analysed not only the first observational
trayed by other observations. Recently the date, but also two other measures of arrival
White Storks from the Western European po- (Sparks et al. 2001). We suggest that the first
pulation (sensu Bairlein 1991) have started to dates are potentially, but not always, good in-
overwinter in their breeding areas (Schulz dicators of arrival time for use in more general
1998, Mata et al. 2001). Moreover, some birds phenological studies. Using three measures of
from the Eastern population have recently be- describing arrival times was possible because
gun to halt their migration in southern Europe, we engaged local farmers in data collection in
notably in Bulgaria (Nankinov 1994), rather areas where White Stork breeds.
than continuing to their traditional wintering Data collected on White Stork phenology
areas in sub-Saharan Africa (Berthold et al. are not biased by weekend effort, as noted for
2001). Hence, at least some individuals have a other data collected mainly by bird-watchers
shorter migration distance and can return to (Fraser 1997, Sparks 1999). Bogucki (1967)
their breeding areas earlier. White Storks are noted that return rates of record sheets was ca
generally well adapted to survive low tempera- 65 % and concluded that good quality data col-328 Journal fuÈr Ornithologie 144, 2003
lected in this way were suitable for studying Beklova, M., Pikula, J., & Sabatka, L. (1983): Phe-
phenology and other aspects of breeding eco- nological maps of bird migration. Acta Sc. Nat.
logy. This may be a consequence of the identi- Brno 17: 1±47.
Berthold, P. (1991): Patterns of avian migration in
fication and appreciation of the White Stork by
light of current global `use's: a central European
a sector of the general public (Lewandowski & perspective. Acta Congr. Int. Orn. 20: 780±786.
Radkiewicz 1991). In our study recorders were Berthold, P., van den Bossche, W., Fiedler, W., Gor-
sent record sheets and feedback in subsequent ney, E., Kaatz, M., Leshem, Y., Nowak, E. &
years. Data were originally sent by post, but Querner, U. (2001): Der Zug des Weiûstorchs (Ci-
from 2001 we added options for transmission conia ciconia): eine besondere Zugform auf
of data by e-mail, phone and fax and hope to Grund neuer Ergebnisse. J. Orn. 142: 73±92.
engage new recorders in this way. We believe Bogucki, Z. (1967): [Some remarks on inquiry
method of investigations of birds.] Przegl. Zool.
this system of data collection to be very useful
11: 161±164.
because it allows us to obtain population data
Creutz, G. (1985): Der Weiûstorch Ciconia ciconia.
that would either be impossible to collect or Wittenberg Lutherstadt.
would incur great cost. Fraser, P. (1997): How many rarities are we missing?
In conclusion, this work suggests that, in stu- Weekend bias and length of stay revisited. Br.
dies of avian migration and its changes over Birds 90: 94±101.
time, the relationship between detection of the Hughes, L. (2000): Biological consequences of
first arrival and population size may not al- global warming: is the signal already apparent?
ways be linked. This fact inspires greater con- Trends Ecol. Evol. 15: 56±61.
Lewandowski, A. & Radkiewicz, J. (1991): [Bocian
fidence in the value of long-term data, at least
w mowie i folklorze ± The stork in language and
for species known to the general public, with- folklore.] Zielona GoÂra. (In Polish)
out detailed data on population size. Data col- Mata, A. J., Calvin, M., Michard-Picamelot, D.,
lected by (well trained) local people can provi- Ancel, A. & Le Maho, Y. (2001): Are non-
de a valuable resource in monitoring bird migrant white storks (Ciconia ciconia) able to
populations. In this study we conclude that survive a cold-induced fast? Comp. Biochem.
aspects of the arrival pattern of White Stork Physiol. 130 A: 93±104.
have changed in recent years. Notably there Nankinov, D. N. (1994): Wintering of the White
Storks (Ciconia ciconia) in Bulgaria. Ring 16:
has been a change in the dates of the earlier ar-
159±168.
rivals, associated with increased temperature,
Norusis, M. J. (1994): SPSSâ 6.1. Base System
and a change in the distribution pattern of User's Guide. Chicago, Illinois.
arrivals. The consequences, if any, of these Profus, P. (1986): Zur Brutbiologie und Bioenergetik
changes to the population dynamics of the des Weiûstorchs in Polen. Beih. VeroÈff. Natur-
White Stork remain to be investigated. schutz Landschaftspflege Bad.-WuÈrtt. 43: 205±
220.
Ptaszyk, J. (1994): [Spring arrival of the White Stork
Acknowledgements Ciconia ciconia in Wielkopolska in 1983±1992.]
We thank all the farmers who participated in this study, Jer- Prace Zakøadu Biologii i Ekologii PtakoÂw UAM
zy Karg for access to meteorological data, Ian Newton for 3: 149±164.
comments on an earlier draft of the manuscript and Wolf-
Ptaszyk, J. (1994a): [Population of the White Stork
gang Fiedler with help with the German translation.
Ciconia ciconia in the former District of PoznanÂ
in 1983±1992.] Prace Zakøadu Biologii i Ekologii
References PtakoÂw UAM 3: 91±118.
SchuÈz, E. (1944): Nest-Erwerb und Nest-Besitz
Bairlein, F. (1991): Population studies of White beim Weiûen Storch. Z. Tierpsychol. 6: 1±25.
Storks (Ciconia ciconia) in Europe. In: Perrins Schulz, H. (1998): Ciconia ciconia White Stork.
C. M., Lebreton J-D., Hirons G. J. M. (eds.): Bird BWP Update 2: 69±105.
Population Studies. Relevance to conservation Sliwinsky, U. (1938): Isopiptesen einiger Vogelarten
and management: 207±229. Oxford. in Europa. Zool. Polon. 2: 249±287.J. Ptaszyk et al. ´ Arrival of White Stork in Poland 329 Sokal, R. R. & Rohlf, F. J. (1995): Biometry. 3rd ed. Tryjanowski, P., Kuzniak, S. & Sparks, T. (2002): New York. Earlier arrival of some farmland migrants in Sparks, T. H. (1999): Phenology and the changing western Poland. Ibis 144: 62±68. pattern of bird migration in Britain. Int. J. Biome- Zabøocka, T. (1959): [Ankunftstermine des Weiûen teorol. 42: 134±138. Storches, Ciconia ciconia (Linn.) in Polen in den Sparks, T. H., Roberts, D. R. & Crick, H. Q. P. Jahren 1946±1952.] Acta orn. 5. 283±299. (2001): What is the value of first arrival dates Zalakevicius, M. & Zalakeviciute, R. (2001): Global of spring migrants in phenology? Avian. Ecol. climate change impact on birds: a review of re- Behav. 7: 75±85. search in Lithuania. Folia zool. 50: 1±17. Tryjanowski, P. & Sparks, T. (2001): Is the detection of the first arrival date of migrating birds influen- ced by population size? A case study of the red- backed shrike Lanius collurio. Int. J. Biometeo- rol. 45: 217±219. Accepted: 04 February 2003
You can also read
