Notes: Summary In February 1992, a study area (A 66) with 310 nestboxes was installed along the construction line of a four laned motorway between Steinau and Schlüchtern (5021'N, 0931'E). One area in the immediate neighbourhood (VG1) and one 5 km distant (VG2) from the study area at the motorway (see Fig. 1) served as controls for comparison. In all three areas, the nestboxes were checked weekly during the breeding season from the beginning of May until July. Species composition of the birds using nestboxes, rate of occupation of nestboxes, and, for Great Tits (Parus major) and Blue Tits (P. caeruleus), date of the first egg, clutch size, hatching rate and number of birds fledged were recorded. The study included 5 breeding seasons from 1992 to 1996, 3 years during the period of construction and 2 years after the opening of the motorway to traffic in December 1994. In 1996, the nestling weight of 20 broods of Great Tits at the A66 was recorded daily and compared with that of all nestlings in another study area (VG3, see Fig. 1). The data were analyzed separately for each year. Distributions of frequencies were analyzed with the x2 test, the other data with the Kruskal-Wallis-Test (H-Test). In case of significant differences between the study areas, the Mann Whitney U-test was used to determine which study area differed from the others. Nestlings bodymass was compared using the t-test. The species composition was similar in all three areas (Fig. 2), and it did not change after the opening of the motorway to traffic. The rate of occupation of the nestboxes, dates of laying of the first egg, clutch size, hatching rate and breeding success vary between years and between study areas (Table 1 to 5); data that differ significantly from those of two other areas are indicated by bold print. Such differences were observed in various years and involved all three areas. In study area A66, clutch size of Great Tits was higher in 1993; hatching success of Great Tits was lower in 1994 and that of Blue Tits was lower in 1993. However, there was no general trend that area A66 at the motorway was different from the other areas, either before or after being opened to the traffic. The weight of nestlings in study area A66 at the motorway was similar to that in comparable area nearby; only on day 12 and 13 after hatching was it slightly lower (Tab. 6). The last measurement on day 15 indicates a nestling weight of 16.2 g for the area at the motorway, which is in normal for deciduous forest habitats and approximately 2 g higher than that recorded in urban habitats. In brief, the motorway did not affect the species composition, rate of occupied nestboxes or the various breeding parameters; in particular, the moving traffic after opening did not seem to have any effect. The breeding parameters from the study area at the motorway were typical for the Schlüchtern region. Density reductions in breeding populations, as discussed by several authors, or disturbances caused by moving traffic, as previously reported, were not observed in our study. However, our key species, Great Tits and Blue Tits, are not generally very sensitive to interferences. Also, the level of traffic on the motorway was still rather low. This must be considered when our findings are generalized.

Notes: Zusammenfassung In 7 Untersuchungsgebieten ließ sich ein signifikanter Anstieg im Eivolumen mit zunehmender Höhe nachweisen (Tab. 1). Hingegen wurde die geringste Gelegegröße in einem isolierten Stadtbiotop ermittelt; eine Zu- oder Abnahme der Gelegegröße in Abhängigkeit von der Höhe der Untersuchungsgebiete konnte nicht festgestellt werden (Tab. 2). Der Bruterfolg war im Stadtbiotop (100 m) und im höchstgelegenen Gebiet (875 m) im Vergleich zu Laubund Nadelwäldern in 300 m Höhe sehr niedrig (Tab. 3). Lediglich in der isolierten Stadtpopulation ließ sich eine reduzierte Gelegegröße als Anpassung an die sehr ungünstigen Ernährungsbedingungen erkennen. In der Höhe wird offenbar durch den ständigen Zustrom aus Tallagen eine Anpassung der Gelegegröße an die Höhenbedingungen verhindert. Als Anpassung an die klimatisch schwierigen Bedingungen in größeren Höhen ist die Zunahme der Eigröße mit der Höhe zu werten. Wegen des hohen Genflusses ist diese Anpassung vermutlich nicht genetisch fixiert.