Since the early 1960s it has been held that migrating birds deposit and use only fat as fuel during migratory £ight, with the non-fat portion of the body remaining homeostatic. Recent evidence from ¢eld studies has shown large changes in organ sizes in fuelling birds, and theory on fuel use suggests protein may be a necessary fuel during £ight. However, an absence of information on the body condition of migrants before and after a long £ight has hampered understanding of the dynamics of organs during sustained £ight. We studied body condition in a medium-sized shorebird, the great knot (Calidris tenuirostris), before and after a £ight of 5400 km from Australia to China during northward migration. Not only did these birds show the expected large reduction in fat content after migration, there was also a decrease in lean tissue mass, with signi¢cant decreases in seven organs. The reduction in functional components is re£ected in a lowering of the basal metabolic rate by 46%. Recent £ight models have tried to separate the`£exible' part of the body from the constant portion. Our results suggest that apart from brains and lungs no organs are homeostatic during long-distance £ight. Such organ reductions may be a crucial adaptation for long-distance £ight in birds.
Is long-distance bird flight equivalent to a high-energy fast? Body composition changes in freely migrating and captive fasting great knots Battley, PF; Dietz, MW; Piersma, T; Dekinga, A; Tang, Sixian; Hulsman, K Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. ABSTRACTWe studied changes in body composition in great knots, Calidris tenuirostris, before and after a migratory flight of 5,400 km from northwest Australia to eastern China. We also took premigratory birds into captivity and fasted them down to their equivalent arrival mass after migration to compare organ changes and nutrient use in a low-energy-turnover fast with a high-energy-turnover fast (migratory flight). Migrated birds were as economical as any fasting animal measured yet at conserving protein: their estimated relative protein contribution (RPC) to the energy used was 4.0%. Fasted birds had an estimated RPC of 6.8% and, consequently, a much lower lean mass and higher fat content for an equivalent body mass than migrated birds. Lean tissue was catabolized from most organs in both groups, except the brain. Furthermore, a principal components biplot showed that individuals were grouped primarily on the basis of overall organ fat or lean tissue content rather than by the size of specific organs. This indicates that organ changes during migratory flight are similar to those of a lowenergy fast, although the length of the fast in this study probably
Loss of rainforest because of agricultural and urban development may impact the abundance and diversity of species that are rainforest natives. Tropical fruit flies are one group of such organisms indigenous to rainforests. In southeast Queensland, a region subject to rapid urbanization, we assessed the impact of habitat disturbance on the distribution and abundance of native fruit flies. Data on four species (Bactrocera tryoni, Bactrocera neohumeralis, Bactrocera chorista, and Dacus aequalis) were gathered and analyzed over 6 months in three habitat types: suburbia, open sclerophyll forest, and rainforest. We also analyzed the data at a combined "dacine fruit fly" level incorporating all fruit fly species trapped over the period of study (as might occur in a biodiversity assessment): these included the four species already named and Bactrocera melas, Bactrocera bryoniae, Bactrocera newmani, and Dacus absonifacies. Analysis at the species level showed that the polyphagous pest species responded differently to the monophagous species. Bactrocera tryoni, which has more exotic than native hosts, was positively affected by transformation of natural habitat into suburbia whereas B. neohumeralis, which has nearly identical numbers of native and exotic hosts, was found equally across habitat types. Bactrocera chorista and Dacus aequalis, each monophagous on a species-specific rainforest host plant, were most abundant in rainforest. The analysis based on the combined data suggests that replacing rainforest with suburbia has a neutral, or even positive, effect on the abundance of fruit flies as a whole. At the species level, however, it can be seen that this is an erroneous conclusion biased by the abundance of a single pest species. Our discussion raises the issue of analyses at supraspecific levels in biodiversity and impact assessment studies.
The distribution of eggs and larvae of Aedes vigilax was studied on part of a coastal saltmarsh in south-east Queensland. At the macroscale (8 ha area), the largest numbers of larvae hatched were from samples taken in areas with relatively low open vegetation adjacent to drainage channels. Such areas are likely to be suitable for egg conditioning and hatching and are also accessible to adult mosquitoes. At the micro-scale (the environs of two small pools), most hatching occurred in narrow bands at specific elevations from the pool bottom but the relationship with vegetation was variable. Failure to hatch larvae from samples taken at the start of, or during, the cooler months was thought to be associated with egg diapause. At the macro-scale whilst the marsh was flooded, most larvae were found in two habitat types: the tall dense Sporobolus virginicus in relatively elevated locations and in depressions dominated by Sarcocomia quinqueflora. At the meso-scale (on a 1.4 ha grid) the distribution of larvae was found to be further related to water tnovetnent. Most larvae were in areas of slower water movement and appeared also to be redistributed by tides.
Great Knots (Calidris tenuirostris) make one of the longest migratory flights in the avian world, flying almost 5500 km from Australia to China during northward migration. We measured basal metabolic rate (BMR) and body composition in birds before and after this flight and found that BMR decreased 42%. The mass-specific BMR based on lean mass decreased 33%. We also starved a group of pre-migratory Great Knots in captivity to determine whether they showed the same reduction in BMR without having undergone the hard work of flight. The captive birds showed a similar range and reduction of BMR values as the wild birds. Exponents of relationships between BMR and body mass in different comparisons were high, indicating large changes in BMR as a function of body mass. Analysis of the body composition of ten wild and three captive birds found that the flight muscle mass and intestine mass positively correlated with BMR. La Tasa Metabolica Basal Disminuye durante Vuelos Migratorios de Larga Distancia en Calidris tenuirostris Resumen. Calidris tenuirostris realiza uno de los vuelos migratorios más largos entre las aves, volando desde Australia hasta China durante la migración al norte. Medimos la tasa metabólica basal (TMB) y la composición corporal en aves antes y después del vuelo y encontramos que TMB se reduce en 42%. La TMB específica por masa, o sea la TMB corregida por masa magra, se redujo en 33%. También expusimos un grupo premigratorio de Calidris tenuirostris a un periodo de ayuno en cautiverio, para determinar si mostraban una tasa de reducción similar en la TMB sin haber soportado la dura tarea de volar. Las aves en cautiverio mostraron un rango y una reducción de los valores de la TMB similares a los de las aves en libertad. Los exponentes de la relación entre TMB y masa corporal en diferentes comparaciones fueron altos, indicando grandes cambios de la TMB en función de la masa corporal. El análisis de la composición corporal de diez aves libres y tres en cautiverio mostró que la masa de los músculos del vuelo y la masa de los intestinos esta positivamente correlacionada con la TMB.
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