Century-long stomatal density record of the nitrophyte, Rubus spectabilis L., from the Pacific Northwest indicates no effect of changing atmospheric carbon dioxide but a strong response to nutrient subsidy.

Triangle Island on Canada's Pacific coast is home to a large, globally important seabird breeding colony. The shrub Salmonberry Rubus spectabilis and tussock-forming Tufted Hairgrass Deschampsia cespitosa together form ~70% of vegetation coverage and contain the vast majority (~90%) of seabird nesting burrows. Salmonberry has in recent decades greatly expanded its coverage, while that of Tufted Hairgrass has receded. Seabirds prefer not to burrow under Salmonberry, making its ongoing expansion a potential conservation issue. We investigated three hypotheses proposed to explain Salmonberry's expansion (climate change, biopedturbation, and nutrient input), using comparisons of stomatal density of Salmonberry leaves sampled from Triangle Island, other seabird colonies, other coastal locations, and from historical specimens in herbaria. Stomatal density helps regulate photosynthetic gain and control water loss, and responds to light, nutrient, carbon dioxide, and water availability. Differing patterns of stomatal density are expected among sample locations depending on which of the hypothesized factors most strongly affects Salmonberry's performance. Our data are most consistent with the nutrient input hypothesis. We discuss possible reasons why Salmonberry has expanded so recently, even though Triangle has been a large seabird colony for at least a century and likely much longer.

Nest-site safety predicts the relative investment made in first and replacement eggs by two long-lived seabirds.

Comparative studies of birds suggest that differences in nest-site characteristics, such as between open-nesting and cavity-nesting species, might ultimately underlie much interspecific variation in clutch size and renesting capacity. The "renesting hypothesis" holds that in species that typically enjoy high breeding success because they nest in safe sites, individuals maximize fitness by laying large first clutches early in the season while withholding few resources for renesting attempts. We tested whether differences in nesting habits would be associated with differences in egg size and renesting capacity in razorbills (Alca torda) and Brünnich's guillemots (Uria lomvia), long-lived marine birds of the tribe Alcini (family Alcidae) that lay single-egg clutches. Razorbills nest in a dispersed fashion, often building nests of small stones and other matter in enclosed crevices where their eggs and chicks are safe from avian predators. Brünnich's guillemots nest very densely on exposed cliff ledges and do not build nests. Due to these differences in nesting habits, razorbills experience higher hatching success than Brünnich's guillemots. As predicted by the renesting hypothesis, razorbills laid larger eggs than guillemots, after accounting for differences in adult body mass. Associated with this larger investment in first eggs, razorbills were less likely than guillemots to replace lost eggs, and they took longer to do so. As these results were obtained by experimentally removing eggs from early-laying females, they presumably assessed the tendencies of more capable birds in both species. Data from other colonies and years were consistent with these results. We conclude that differences in nesting habits have led to evolutionary divergence in the investment made in first and replacement eggs by these two closely related species.