Stromal pigments from the irises of 28 species of birds having brightly colored eyes were extracted and analyzed. Carotenoids were present in six species and they were the sole bright pigment in only two of these. The iris pigments of the majority of the birds examined were soluble in 0.1 M NaOH and chromatographic analysis indicated they were primarily pteridines and purines. The pteridines often occurred in a crystalline state, either alone or, more commonly, in conjunction with purines.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology. Abstract. We examined the effect of age on breeding performance in male and female Merlins (Falco columbarius) from a natural population using a long-term data set. In the analysis, we examined whether differences in chick hatch date and brood size associated with parents of different ages arose due to selection of superior individuals (differential mortality hypothesis) or to changes within individuals over time (inadequate experience hypothesis). In addition, we examined the effect of longevity on production of recruits and lifetime reproductive success (LRS). In both sexes, breeding performance improved with age. In females, this was mainly the result of disproportionate mortality of inferior breeders, with less evidence to support performance changes within individuals. Among males, changes in breeding performance with age were largely the result of improvements within individuals early in their life (between age 1 and 2 +). Production of recruits was not dependent on parental age at the time of breeding for either sex. Recruit production and LRS were both influenced by longevity, so that longer-lived birds produced more offspring over their lifetimes and thereby had a greater probability of producing recruits. The differences between the sexes in terms of age-dependent breeding performance are likely a consequence of the differing roles the two parents play in reproduction. Male Merlins provide most of the food for the pair and their young during the breeding season, and changes in hunting skill with age may account for individual improvements in breeding performance.

We studied the breeding ecology of Merlins (Falco columbarius) in Saskatoon, Saskatchewan, Canada, from 1971 to 1990. The nesting population increased from 1 pair in 1971 to a maximum of 31 pairs in 1989. At 25.4 pairs/100 km2, the 1989 nesting density is the highest recorded for this species. The population increased at a rate of 0.165 ± 0.015, or 17.9%, per year. The growth rate of the population declined, although not significantly, with increasing density. Merlins spaced their nests regularly, with nearest-neighbour distances ranging from 161 to 4669 m. Clutches were initiated between 19 April and 29 May. Earlier clutches had more eggs and produced more young. Weather did not appear to influence the breeding phenology, but fledgling House Sparrows (Passer domesticus, the primary prey) were maximally available when Merlins had their chicks. The reproductive success of this population was one of the highest recorded for this species. In only 4% of the nests did any eggs fail to hatch. The mean and modal clutch sizes were 4.2 ± 0.04 (SE) and 5, respectively, and mean and modal brood sizes were 3.8 ± 0.03 and 5, respectively. We did not observe any significant effect of nesting density on either clutch or brood size. Males delivered most of the food and were most active in nest defence against corvids, while females primarily incubated, brooded, and fed the nestlings. This expanding Merlin population had higher and more consistent reproductive rates than other populations.

This paper reviews evidence for the presence of pteridines in iridophores, leucophores, and xanthophores in a wide variety of vertebrate chromatophores, and argues that the chemical and functional distinction between pterinosomes and reflecting platelets is not as clear-cut as previously believed. Observations indicate that: (1) Pteridines may, either alone or in conjunction with purines, form pigment granules that reflect light, (2) these pigment granules are highly variable ranging from fibrous pterinosomes to typical reflecting platelets and may be colored, reflect white light, or be iridescent, and (3) many "leucophores" probably contain typical pterinosomes and presumed associated colorless pteridines and are therefore more closely related to erythrophores and xanthophores than to iridophores with which they are usually classified. We propose that the classification of pigment cells should be modified to reflect these facts.