Growth and Development of the Rufous-Winged Sparrow (Aimophila carpalis)

Growth and dcvclopment of birds have engendered considerable recent interest.Rate of increase in body weight is known for many species (Ricklefs 1968a, 1972), but development of homeothermy (e.g., Kendeigh 1939, Dawson and Evans 1957, 1960, Ricklefs and Hainsworth 1968), relative growth of organs and changes in body composition (Ricklcfs 1967a, 1975, Myrcha and Pinowski 1969, Diehl et al. 1972) are poorly known.Few attempts have been made to correlate all these factors in one species (Diehl et al. 1972, Diehl and Myrcha 1973, Ricklefs 1975).Herein, we compare growth and development of the Rufous-winged Sparrow ( Aimophila carpalis), which has a short nestling period (8-9 days), to those of the Cactus Wren ( Campylorhynchus brunneicapillus), with a nestling period of 20 days (described in detail by Ricklefs and Hainsworth 1968 and Ricklefs 1975).METHODS The Rufous-winged Sparrow is a locally common resident of shrubby grasslands in southern Arizona and Sonora, Mexico.Its life history has been described by Ohmart ( 1969).Growth, development of homeothermy, and behavioral changes in nestlings of known age were studied during July, August and September, 1970 and 1971, on the Santa Rita Experimental Range, Pima County, Arizona.Young were weighed and measured between 05:OO and 09:OO.We measured the bill (from nares), wing (flesh only), wing chord, length (exposed) of third primary, tarsus, length (exposed) of second rectrix, and width of flange.Sequence of feather eruption, age at eye opening, and changes in behavior were noted.To study development of homeothermy, we removed nestlings from their nests and took their body temperature (Tr,, proventricular) with a Schultheis quick-registering thermometer.We then placed them in a portable ice chest containing two half-gallon containers of ice for 40-45 min.Air temperature in the ice chest could be maintained below 25°C and remained relatively constant (i-1°C in 11 trials, checking temperatures at 5min intervals ).Birds were insulated from direct contact with the ice by at least 2 cm of newspaper.Body temperature was taken immediately on removal of the bird from the chamber, and the nestlings were returned to their nest.Fourteen nestlings of known age, five juveniles, and three adults were collected in the same general area for analysis of constituents and organ weights following the methods described in Ricklefs (1967aRicklefs ( , 1975)).Wet weight minus dry weight is the water content; dry weight minus lean dry weight is the lipid content.Wing areas were obtained by tracing the outline of the extended wing onto paper and weighing the outlined portion.Wing loading, expressed as g/cm?, was calculated as body weight divided by the area of both wings.An ash index was calculated for Rufous-winged Snarrows as the ash weight of head.bodv.legs and Austin and Ricklefs: Growth and Development of the Rufous-winged Sparrow (aimophila Ca