Survey data on seabird distribution at sea, hydrographic data and optical satellite data collected for the German Bight were used to analyse the variability of the distribution of wintering redthroated diver and black-throated diver Gavia stellata/arctica in relation to oscillations of the Jutland Coastal Current (JCC) and associated surface fronts. Data collected from hydrographic stations were summarised by means of principal component analysis; the first component, reflecting characteristics of the JCC, provided a satisfactory quantitative measurement of the average meso-scale habitat used by both species. The pelagic range of divers clearly followed the outer estuarine front between surface North Sea water and the JCC, which was located between the 20 and 30 m depth contours. Despite a highly transient trailing edge of the JCC, no divers were ever observed in North Sea water. Hydrographic as well as composited satellite CZCS (Coastal Zone Color Scanner) data indicated the presence of an inner front, spanning a stronger surface salinity gradient than the outer estuarine front. The inner estuarine front was located between mixed estuarine water, with salinities between 32 and 34 psu, and the core of the estuarine water mass from the river Elbe, with salinities below 32 psu. Seven-year composite images, produced from all available CZCS-Chl (chlorophyll) data taken over the German Bight during the Nimbus-7 mission, revealed the mean distribution of the inner estuarine front as a sharp gradient between the 15 and 20 m depth contours, extending less than 10 km in longitude. The variability of the inner estuarine front was measured over a series of cruises, and it indicated a quasi-stable structure; the prevailing position of the surface front was in a zone stretching from 07°30' E at Horns Reef (55°45' N) to 07°50' E south of Amrum Bank (54°30' N), except during easterly winds when the front was advected offshore as far as 6°50' E. The recorded patches of high densities of divers were almost confined to areas within 5 km distance from the mean frontal zone. The link between divers and the inner estuarine front seemed rather persistent, as peak densities coincided with the location of this front during all cruises, while lower densities were normally observed in the core Elbe water and in the mixed water outside the front. The authors suggest that the quasi-stability and strength of the inner estuarine front give rise to a predictable location of food resources (i.e. small fish) for divers in the German Bight. Our study highlights the potential for frontal structures of the JCC to influence the marine ecosystem of the southeastern North Sea.KEY WORDS: Estuarine fronts · German Bight · Seabird foraging · Red-throated/black-throated diver · Gavia stellata/arctica Resale or republication not permitted without written consent of the publisher

Evaluating habitat suitability is often complex, as habitat effects may be scale-dependent, critical resources may be spatially segregated, and resource availability may also depend on intra-and inter-specific interactions. Using analyses that spanned multiple years and spatial scales, we investigated habitat requirements of a territorial generalist, the common raven Corvus corax, in a relatively pristine woodland, Bial owieża Forest (E Poland). We compiled data from multiple raven surveys conducted between 1985 and 2001. Ravens were regularly distributed over the entire study area but declined in density over 50% within the 16 yr interval. In the same period game and forest management significantly reduced ungulate densities and likely diminished the habitat quality with regard to food supply, especially carrion. To better understand habitat requirements of ravens we studied breeding performance in relation to three different habitat types across multiple scales: open areas, coniferous-dominated forest, and deciduous-dominated forest. We found a prominent dissimilarity between raven nesting and foraging habitats highlighting the importance of resource complementation for ravens. On a fine scale, large old pines were exclusively selected as nesting trees and nesting areas were generally coniferous-dominated. However, at increasingly broader scales, coniferous habitats were negatively associated with raven reproductive success as those habitats likely provide a lower food supply. Only where the coniferous nesting areas at smaller scales were complemented with high percentages of deciduous forests and open areas at broader scales did the breeding performance increase. In addition to habitat composition, intra-specific interactions were important determinants of reproductive performance and very successful neighbors decreased reproductive performance of a focal pair. Most of previous studies have investigated resource complementation in terms of habitat edges or proximity of complementing resource patches. Our study demonstrates that the concept of landscape complementation also applies to gradients in landscape composition and emphasizes the importance of scales and intraspecific interactions in habitat analyses.

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The Swahilian Coastal Forests in eastern Africa are recognised to be a globally important habitat containing large numbers of endemic species, yet are still poorly known over much of their extent. Floristic diversity and endemism in these forests appears to peak in SE Tanzania, where only a few forests have hitherto been surveyed. We carried out a digital analysis of Landsat Thematic Mapper (TM) data to identify other potential areas of Coastal Forest in Lindi and Kilwa Districts, SE Tanzania, followed by a field survey to ground truth and fine-tune our analysis. Our analysis has identified, mapped and sub-classified all remaining areas of Coastal Forest in Lindi and Kilwa Districts, and includes the discovery of a large and hitherto undescribed area of Coastal Forest at Namatimbili, which would make it one of the largest known blocks of contiguous Coastal Forest in eastern Africa. This forest furthermore appears to be minimally impacted by human disturbance. Given the rapidly increasing threats to forested vegetation in this area, urgent efforts are required by the conservation community to ensure the immediate and continued protection of Namatimbili forest.