Migration of Little Stint (Calidris minuta) at Eilat, Israel Reuven Yosef International Birding & Research Center in Eilat, P. O. Box 774, Eilat 88000, ISRAEL Przemek Chylarecki Gdansk Ornithol. Station, Nadwislanska 108, PL-80-680 Gdansk 40, POLAND Piotr Tryjanowski Dept. of Avian Biol. & Ecology, A. Mickiewicz Univ., PL-61-701 Poznan, POLAND

Migration similar to other Calidris species? Migration & over-wintering Sexual differences – Males migrate earlier?

Sex ratio of wintering birds larger winter more northerly? Males closer to breeding grounds?

Age, sex – adult M/F, juvenile M/F Phenology in Julian dates

Bill length was calculated from total-head length as the two variables are highly correlated in Little Stints (r2 = 0.71) & enables a relatively accurate prediction using the formula: bill-length = 0.690*total-head – 8.623 Underhill L.G., Tomkovich, P.S., Chylarecki P., Kania W., Hotker H., Hilden O., Summers R.W., Soloviev M.Y.& van Dijk K. (submitted Ardea) Breeding distribution and biometrics of Little Stints Calidris minuta.

Mass of stored fat estimated using equation developed for Little Stints wintering in NW Africa: fat mass = 0.596* body mass – 0.097*wing length ­– 1.69 (r2 = 0.86; Piersma T. & Van Brederode N.E. 1990. The estimation of fat reserves in coastal waders before their departure from northwest Africa in spring. Ardea 78: 221-236.)

The annual cycle of Little Stints in Israel was divided into four periods: autumn migration wintering spring migration summer with cut-off points selected based on the numbers of birds caught at pentades 43/44 (summer/autumn), 70/71 (autumn/winter), 11/12 (winter/spring) and 30/31 (spring/summer).

Fig. 1. Numbers of Little Stint caught at Eilat by 5-day periods Fig. 1. Numbers of Little Stint caught at Eilat by 5-day periods. Data for 1984-2000; n=4849

Fig. 2. Age composition of Little Stints caught during autumn migration (pentades 44-70, n=3700) in 5-day periods.  

Fig. 3. Variation in percentage of males among Little Stint caught during autumn migration (n=1670).    

Fig. 4. Variation in percentage of males among adult Little Stints caught during summer and autumn migration (n= 950).  

Table 1. Ancova on body mass with month, sex, age and structural size variables Dependent Variable: MASS _________________________________________________________________ Source Type III df Mean Square F Sig Sum of Square Corrected Model 4363.611 23 189.722 22.212 .000 Intercept 73.616 1 73.616 8.619 .003 WING 79.165 1 79.165 9.268 .002 HEAD 337.186 1 337.186 39.477 .000 TARSUS+Toe 323.421 1 323.421 37.865 .000 SEX 7.968 1 7.968 .933 .334 MONTH 1668.595 10 166.860 19.535 .000 SEX * MONTH 52.634 9 5.848 .685 .723 Error 18167.475 2127 8.541 Total 1281362.000 2151 Corrected Total 22531.086 2150 R2 = .194 (Adjusted R2 = .185)

Fig. 5. Annual variation in average body mass of Little Stints by 10-d period. Sexes and ages combined.  

Fig. 6. Variation in frequency of heavy Little Stints, i. e Fig. 6. Variation in frequency of heavy Little Stints, i.e., those with estimated fat stores exceeding 5.5 g. Sexes & ages combined.

Fig. 7. Variation in frequency of very light birds - those with estimated fat stores less than 1.0 g. Sexes & ages combined.  

CONCLUSIONS: * Winter body mass in Israel similar to Little Stints wintering in sub-Saharan Africa in Mauritania (Piersma & Van Brederode 1990) and in Kenya (Pearson 1987). * No increase in mid-winter body mass in birds wintering at Eilat. Similar to waders that winter in northern latitudes.Assumed that these stores act as a buffer against unpredictable weather. In Israel, no need to have such an 'insurance' against inclement weather. *Autumn migration - 66% of birds at Eilat juveniles and is similar to 70% found by Gromadzka (1987) at Gdansk, Poland. On the other hand, on wintering grounds in Kenya, Pearson (1987) found that juveniles comprised 35-50% of the October-December samples.

CONCLUSIONS (continued): * Greater body mass in autumn suggests a long non-stop flight. * Negative fat stores obviously emaciated owing to catabolism of structural proteins. *Biased sex ratio in favor of males suggests Little Stint females use other migration routes or wintering grounds than males of the same population.

* Possible that the discriminant function developed for Siberian Little Stints by Underhill et al. is not valid for the population migrating through Israel, and inflates the proportion of males in a sample. *Pronounced seasonal variation in sex ratio among adult Little Stints on autumn migration: species' breeding system??

Fig. 4. Variation in percentage of males among adult Little Stints caught during summer and autumn migration (n= 950).

(From: Int. Wader studies 10. 1998.) *Eilat