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Facultative Altitudinal Movements by Mountain White-Crowned Sparrows (Zonotrichia Leucophrys Oriantha) in the Sierra Nevada
Get PDFMountain White-crowned Sparrows (Zonotrichia leucophrys oriantha) winter in Mexico and often arrive in the vicinity of their breeding grounds in the Sierra Nevada well before nesting is possible. Arrival at Tioga Pass, California (elevation 3,030 m), usually occurs in early May, but residual winter snow and adverse weather can delay nesting for weeks. We used radiotelemetry to determine whether prebreeding Mountain White-crowned Sparrows engaged in weather-related altitudinal movements during the waiting period between the end of spring migration and onset of breeding during 1995-2001, with a range of residual winter snowpacks. Interannual variation in arrival date and onset of egg laying was 18 and 41 days, respectively. We tracked females for two years and males for all seven years. During spring snowstorms (which occurred in four years), radiomarked individuals moved to lower elevation sites, where they often remained for several days. Departing birds left Tioga Pass by early afternoon and returned early in the morning after storms. More frequent storms during tracking increased the likelihood of facultative altitudinal movements, but heavier residual winter snowpack did not. Warm days increased the likelihood of birds returning to Tioga Pass from low elevation. This study demonstrates that facultative altitudinal movement behavior can be a common feature of spring arrival biology in montane-breeding birds. Received 1 November 2002, accepted 30 June 2004.Integrative Biolog
Survival and mean corticosterone release rates of larval northern leopard frogs (Rana pipiens) per day throughout chronic NaCl exposure experiment
No full textWe investigated the influence of corticosterone release rates on survival of larval Northern Leopard Frogs (Rana pipiens) chronically exposed to four different concentrations of salinity (NaCl). The dataset contains mean values for snout-vent length (mm), mass (g), developmental stage (Gosner stage) and mean log-transformed corticosterone release rates (baseline, stress-induced, and corticosterone increase; pg/h). It also contains survival data in percent surviving, numbers alive and dead, and total number of larvae per day and treatmen
Morphology, survival and corticosterone release rates of larval northern leopard frogs throughout chronic NaCl exposure experiment
No full textWe investigated the influence of increased salinity on survival, growth, water content, and Corticosterone responses of larval Northern Leopard Frogs (Rana pipiens) by exposing them to environmentally-relevant salinity treatments for 24 days. We also inhibited Corticosterone for half of the replicates using mifepristone to determine if Corticosterone mediates effects of salinity and tradeoffs between traits
Survival of larval northern leopard frogs (Rana pipiens) throughout chronic NaCl exposure experiment
No full textWe investigated the influence of chronic exposure to four different concentrations of salinity (NaCl) on survival of larval Northern Leopard Frogs (Rana pipiens) across 24 d. We also assessed if corticosterone mediates lethal effects of NaCl by inhibiting actions of corticosterone for half of the larvae in each treatment using mifepristone (a glucocorticoid antagonist). The dataset contains survival data (percent of larvae surviving) per group and da
Morphology and corticosterone release rates of larval northern leopard frogs (Rana pipiens) per day throughout chronic NaCl exposure experiment
No full textWe investigated the influence of exposure to chronic salinity (NaCl) and mifepristone (a glucocorticoid antagonist) for 24 d on corticosterone release rates (baseline, stress-induced and corticosterone increase) of Northern Leopard Frogs (Rana pipiens). The dataset contains per-individual, per-day values for snout-vent length (mm), wet mass (g), developmental stage (Gosner stage), log-transformed corticosterone release rates (baseline, stress-induced, and corticosterone increase; pg/h), and mass-corrected and log-transformed release rates (pg/g/h). It also contains coefficients of determination (%) for each corticosterone release rates calculated following quantification with enzyme immunoassays. Within the dataset, 'Died' indicates if that larvae subsequently died in the experimen
Morphology of larval northern leopard frogs (Rana pipiens) on last day of chronic NaCl exposure experiment
No full textWe investigated the influence of exposure to chronic salinity (NaCl) and mifepristone (a glucocorticoid antagonist) for 24 d on wet mass (g), dry mass (g; following freeze drying), water content (%; calculated after freeze drying), snout-vent length (mm), and developmental stage (Gosner stage) of Northern Leopard Frogs (Rana pipiens). The dataset contains values of each trait for each larva that was alive on the final day (day 24) of the experimen
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An integrated evaluation of costs and benefits of corticosterone secretion through development
Get PDFtextGlucocorticoids (GCs) play critical roles during development: transient increases
in GCs facilitate anticipatory physiological changes and trigger ontogenetic transitions
such as promoting fetal/embryonic organ maturation and initiating birth/hatching. In
contrast, chronically elevated GCs can be detrimental to growth, cognition, and survival.
Thus, animals going through substantial growth may have higher corticosteroid binding
globulin (CBG) levels, or enhance negative feedback/tonic inhibition on the
hypothalamic-pituitary-adrenal (HPA) axis to keep GCs levels low. Here I investigated
these hypotheses using altricial white-crowned sparrow nestlings. I examined 1) the
ontogeny of the corticosterone (CORT) response (both total and free hormone levels), 2)
changes in corticosteroid receptor levels in brain with age, and 3) effects of acute and
extended elevation of CORT on behavior and growth.
In response to acute stress, nestlings showed a low HPA reactivity in total CORT
during the first 1/3 of the nestling period. When free CORT is considered, this
hyporesponsive period was extended to 2/3 of the nestling period, suggesting CBG is one
of the mechanisms to keep free CORT low. These periods coincided with rapid mass
gain and acquiring thermoregulatory ability. The low reactivity was partly due to a
dampened sensitivity at pituitary level or higher as all stages of nestlings responded to
adrenocorticotropic hormone challenges; however it was not due to an enhanced negative
feedback/tonic inhibition on hypothalamus or hippocampus. When CORT levels were
artificially elevated, I only observed detrimental effects on begging behavior and growth.
These series of data elucidated the ontogeny of the HPA axis in altricial nestlings
regarding CORT, binding globulin, and receptor levels. In addition, I found that
measured effects of exogenous CORT are primarily costly and highly age-specific.Ecology, Evolution and Behavio
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