Arrival and Departure Dates
Section snippets
Summary
We review the current evidence that changes in arrival and departure dates of migratory birds have taken place, and the relationship of these changes to climate variability. There is little doubt that the timing of spring migration closely follows weather variations. This is more evident and/or stronger in short-distance migrants than in long-distance migrants, but the latter have also responded to climate change. Changes of spring arrival in birds depend on climate impacts at different
A Brief History
The earliest systematic records on arrival and departure of migratory birds in Great Britain are from the early 1700s (Kington 1988, Sparks and Carey 1995) and in Northern Europe from the mid-1700s (Linné 1757, Leche 1763). These texts mark the start of phenological research, which was one of the earliest organised branches of systematic ornithological observation in many parts of Europe.
It has been well known for hundreds of years that arrivals of migrating birds are good predictors of
Variation of Arrival Dates During the Last 250 Years
The longest continuous time series available for analysis exceed 250 years in length. All these data are observations of first arrivals of bird species that were well known to people of rural communities. In time series approaching or exceeding 100 years (Sparks and Carey 1995, Ahas 1999), it becomes readily evident that the variation of arrival times around the overall average or trend often shows periods of constant direction of change and then a shift in the direction (Figure 2). Correlating
Types and Quality of Data
Different types of arrival information have been used in recent analyses. First arrivals and mean or median arrivals are the most common ones. First arrival (the day on which the first individual of the species is recorded each spring in the area) is most frequently recorded in some countries by local ornithological clubs and in others more systematically by meteorological stations or in programs run by scientific or governmental organisations (von Haartman 1956, Ahas 1999; Sparks and
How is Earlier Arrival Achieved?
For a migratory species, breeding area is by definition different from the wintering area. Therefore, birds cannot respond behaviourally to amelioration of climate in the breeding area unless the climatic conditions in the wintering area and/or in the area through which the species migrate are positively correlated. The longer the migration journey, the less likely high positive correlations in climate between areas crossed will be. Long-distance migrants, furthermore, have to pass over
Statistics
Several simple methods have been used to test whether changes in timing of migration are statistically significant. Some authors have used correlation (arrival vs. year, Pearson or Spearman) others have used linear regression (arrival vs. year) and in still other cases non-parametric smoothing methods have been used for descriptive purposes. In a few cases, multiple regression approaches have also been applied.
The statistical complications, of which one must be aware of, depend partially on the
Confounding Factors
Simple analyses of temperature effect and trend are inevitably coarse. Arrival and departure dates depend on other factors as well. Some of these have been identified and incorporated in the models. We divide the confounding factors in two groups: (1) those depending on the observers, and (2) those depending on birds. An example of the former is the possible trend of observer activity and skill (Sparks et al. 2001, Butler 2003, Vähätalo et al. 2004, but cf.Mason 1995, Tryjanowski et al. 2002),
Overview of Changes of Timing in the Latter Part of the 20th Century
Burton 1995, Zalakevicius and Zalakeviciute 2001, Bairlein and Winkel 2001, Fiedler 2001 have earlier summarised evidence for changes in arrival and departure dates of migratory birds. Impacts on birds have been included also in more general reviews and meta-analyses (Hughes 2000, Root et al. 2003). We give below an overview on the present state of affairs knowing that much work is currently under way and new reviews will soon be needed. We collected published time series of migration times
Consequence of Changing Timing
Large changes in arrival and departure dates may have important consequences for other parts of a species' annual cycle. The final step—a species or an appreciable part of its population becoming sedentary—has also been documented with different example species in different areas (Zalakevicius et al. 1995, Berthold 1998; Fiedler et al., 2004, this volume). Partial migrants are continuously “monitoring” the weather and food conditions and they can be especially fast in taking whatever advantage
Future Work
The quality of data still needs further study. There are several points of concern as pointed out in this review, but despite this, the sign of change and the signal are most likely correct. What needs to be done is to identify and quantify the other factors that cause arrival and departure dates to shift in the same direction as climate and weather. At least in some areas, detectability of first arrivals may have changed and there is no careful analysis on how important a factor this might be.
References (80)
- et al.
Tree
(1999) Tree
(2000)Int. J. Biometeorol
(1999)- et al.
Global Change Biol
(2004) - et al.
Behav. Ecol. Sociobiol
(2000) Bird Migration
(1990)- et al.
- (2002)
Acta Congr. Int. Ornithol
(1991)
Control of Bird Migration
Naturwissenschaftliche Rundschau
Nature
Proc. Natl Acad. Sci. USA
Birds and Climate Change
Ibis
Am. Stat
Ardea
Ecography
Weather and Bird Behaviour
J. Anim. Ecol
J. Orn
Avian Ecol. Behav
Circannual Rhythms: Endogenous Annual Clocks in the Organization of Seasonal Processes
J. Exp. Biol
Finnish Game Res
Suomen Riista
Finn. Meteorol. Inst. Contrib
Bird Study
Bird Study
Proc. R. Soc. Lond., Ser. B Biol. Sci
Proc. Natl Acad. Sci. USA
Bird Study
Proc. R. Soc. Lond. B
Specimen calendarii florae et faunae aboensis
Aboæe
J. Clim
Cited by (320)
Estimating population dynamics trajectories of raptors from a multi-species hierarchical distance sampling model
2023, Ecological InformaticsLimited increase in asynchrony between the onset of spring green-up and the arrival of a long-distance migratory bird
2021, Science of the Total EnvironmentCo-migration fidelity at a stopover site increases over time in African-European migratory landbirds
2023, Royal Society Open ScienceMicro-evolutionary response of spring migration timing in a wild seabird
2024, Evolution Letters