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During summer 1991, lemmings occurred at high densities in Arctic tundra at Pronchishcheva Lake in the northeastern Taimyr Peninsula, whereas, in 1992, lemming densities were substantially lower and decreased further during the summer. In 1991, avian predators such as Snowy Owls Nyctea scandiaca, gulls and skuas bred well; Arctic foxes Alopex lagopus were rarely observed in the study area but bred in the immediate vicinity. In both years there was a late thaw, but this did not deter breeding by birds. The insect food supply for waders showed similar patterns of abundance in both years. In 1991, 73 nests of nine species of wader were found within a 14‐km2 study area, and Dark‐bellied Brent Geese Branta bernicla bernicla nested in association with Snowy Owls. The overall density of wader nests was estimated to be 7 per km2. Clutches disappeared at only two wader nests and no Brent Goose nests, and the Mayfield estimate of the daily probability of predation for waders was 0.0022. In contrast, the daily probability of predation was 0.20 in 1992, when there was a similar breeding density of waders. Arctic foxes were seen searching for food daily within the study area, and fox droppings were found associated with nests taken by predators. The predicted scenarios for peak and decreasing lemming years (the Roselaar‐Summers hypothesis), i.e. low predation and high nest success in the peak year and high predation and low nest success in the decreasing year, therefore occurred.

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Diode and DPSS lasers emitting a variety of wavelengths are now commonly incorporated into flow cytometers, greatly increasing our capacity to excite a wide variety of fluorochromes. Until recently, however, virtually no practical technology existed for generating yellow or orange laser light for flow cytometry that was compatible with smaller instrumentation. In this study, we evaluate several new solid state laser systems that emit from the 570 to 600 nm as excitation sources for flow cytometry. DPSS 580, 589, and 592 nm sources were integrated into a cuvette-based flow cytometer (BD LSR II) and a stream-in-air cell sorter (FACSVantage DiVa), and used to excite a variety of yellow, orange, and red excited fluorochromes, including Texas Red, APC, and its tandem conjugates, and the genetically encoded red fluorescent protein HcRed and the more recently developed Katushka. All laser sources were successfully incorporated into the indicated flow cytometry platforms. The yellow and orange sources (particularly 592 nm) were ideal for exciting Texas Red, and provided excitation of APC and its tandems that was comparable to a traditional red laser source, albeit at higher power levels than red sources. Yellow and orange laser light was optimal for exciting HcRed and Katushka. Practical yellow and orange laser sources are now available for flow cytometry. This technology fills an important gap in the laser wavelengths available for flow, now almost any fluorochrome requiring visible light excitation can be accommodated. recently produced a variety of novel laser sources that have proven useful for flow and image cytometry (1). These lasers are small and durable enough for integration into small benchtop cuvette-based instrumentation, and often possess sufficient power levels to accommodate stream-in-air cell sorting (2). Ultraviolet (370-380 nm), violet (395-415 nm), and blue (435-445 nm) laser diodes have all been incorporated into flow cytometers and are being used for exciting a wide range of useful fluorescent probes (3-6). DPSS lasers are now available in the blue-green range (473-515 nm), with the DPSS 488 nm variant replacing traditional ion lasers for many instrument applications. Green (532 nm) and green-yellow (561 nm) DPSS lasers have proven useful for efficient excitation of phycoerythrin and its tandems, as well as rhodamine-based fluorochromes and GFP-like long-wavelength fluorescent proteins (2,7,8). These lasers are also starting to appear on commercial flow cytometry instrumentation, vastly improving our ability to utilize the full spectrum of fluorescent probes available for biomedical analysis.However, until very recently, a significant gap existed in the range of laser wavelengths available for flow cytometry. The yellow to orange bandwidth ($570-620 nm) was very difficult to achieve using existing technology. Yellow and orange