It has been shown that small passerines can counteract variability of food resources by actively regulating their body reserves through an increase of mass. However, the effects of food predictability on body mass regulation and other body parameters, such as immune functions, in larger species have been little studied. To analyse the response of the Hooded Crow Corvus corone to food abundance and predictability, we performed three experiments with controlled food provisioning under laboratory conditions. Body mass, TOBEC (total body electrical conductivity) lean mass index, blood parameters and immune organ masses were measured at the beginning and end of a 15‐day period. In the first experiment, the food release was predictable (same amount each day) but the quantity of food delivered to five groups of birds varied (37, 75, 100, 150 or 300 g/day). Low food levels induced a greater decrease in mass accompanied by an increase in erythrocyte sedimentation rate. In the second experiment, the same average quantity of food (100 g) was supplied according to either predictable or unpredictable (random) schedules. In this case, the crows lost more mass, and their erythrocyte sedimentation rate increased when food was unpredictable. In the third experiment, the same average quantity of food (150 g) was supplied according to either a predictable schedule or two schedules with different levels of variability. The group with a low level of variability did not differ from the control, while the group with a highly variable feeding schedule lost more mass. In this group, the higher mass loss was associated with greater variation of the erythrocyte sedimentation rate and a reduced Phytohaemagglutinin index of immunocompetence and haematocrit value. The results of experiments 2 and 3 contrast with findings in other passerines, which increase their mass when food availability is unpredictable. It appears that a body mass decrease in the Hooded Crow can be induced by a reduction of either food abundance (exp. 1) or food predictability (exp. 2, 3), and it is accompanied by a worsening of health state.

Only recently have there been attempts to assess the short-term variations of indices of body conditions and immunocompetence in free-living populations, and to evaluate the presence of significant fluctuations of these indices between years. We compared body conditions and size of immunocompetent organs (spleen and bursa of Fabricius) in wild populations of hooded crows in NW Italy during three years. Differences in population density among sites did not influence any of the variables, while a great difference was found between adult and subadult birds. In the study period, adults did not show any year-related variation of mass, structural size, lean mass (as assessed by TOBEC electroconductivity index), and spleen mass. Instead subadults of both sexes showed differences among years in mass; subadult females had the lowest values of bursa and spleen mass in the year when mass was smallest. The results show that in natural populations between-year variation of body conditions may exist. Subadults are probably most sensitive to adversities producing short-term variations in body conditions.

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1999)Sex identification in the moorhen (Gallinula chloropus) by flow cytometry and morphometric analysisABSTRACT Sexing individuals in a population is important in many ecological and life-history studies. Since many bird species are monomorphic, non-invasive tools are necessary for sex determination. In this study we utilized flow cytometry to sex individuals in a moorhen population of northern Italy. By improving previous laboratory protocols, we were able to obtain clear and repeatable measures of DNA content from field blood samples. The per cent difference in nuclear content between male and female moorhens was among the highest values reported for birds. We also utilized a discriminant analysis of seven morphological measures to investigate whether birds can be sexed on the basis of biometry. Tarsus and foot lengths were the most influential variables in gender discrimination. However, only 13 females and 10 males (77%) were correctly sexed, while six females and two males were wrongly assigned. When juvenile moorhens were excluded the discriminant analysis correctly sexed 90% of the birds. Since morphometric comparisons with English moorhen populations showed that discriminant biometrical values are geographically different, and thus not useful as universal sexing tools, we recommend the use of the cytometry technique for sex determination.

SummaryLittle is known about indices of health condition in free-living populations and particularly about the presence of significant fluctuations of these indices between years. We assessed blood and immunological condition in wild Hooded Crows (Corvus corone cornix) in NW Italy for three years (1997)(1998)(1999). Crows did not show any year-to-year difference in erythrocyte sedimentation rate, leukocyte abundance, and heterophyl/lymphocyte ratio. In contrast, we observed significant annual differences in albumin and immunoglobulin values. The albumin/immunoglobulin ratio was lower in 1998, a year when the size of two immunocompetence organs (bursa of Fabricius and spleen) was also smallest. Neither population density nor climate were likely to affect the observed variation of immune condition, annual censuses not revealing any noticeable density variation during the study period, and rainfall and mean temperatures being similar. The results show that in natural populations between-year variation of immune condition may exist, and that in our study, species immunoglobulin assays were more effective than leukocyte counts to detect them.Keywords: erythrocyte sedimentation, heterophyl/lymphocyte ratio, immunoglobulin, immunocompetence. Zusammenfassung JShrliche Variation immunologischer Parameter bei Nebelkriihen (Corvus corone cornix)0ber Parameter, die den Gesundheitszustand freilebender V6gel indizieren, ist nur wenig bekannt. Wit haben immunologische Parameter yon Nebelkr~ihen (Corvus corone cornix) in NW Italien tiber drei Jahre (1997)(1998)(1999) verfolgt. Die Kriihen zeigten keine jiihrliche Variation in der Erytrozytensenkungsgeschwindigkeit, in der Zahl der Leukozyten oder im Heterophilen/Lymphozyten-Verh~iltnis. Signifikante j~ihrliche Schwankungen gab es jedoch in den Albumin-und Immunoglohulinwerten. Das Verh~iltnis yon Albumin zu Immunoglobulinen war am geringsten in 1998, in dem Jahr in dem die Gr613e zweier immunkompetenter Organe (bursa Fabricius und Milz) am kleinsten war. Weder die Populationsdichte noch das Klima scheinen ftir diese Schwankungen verantwortlich zu sein, da beide w~ihrend des Beobachtungszeitraum relativ konstant waren. Unsere Ergebnisse zeigen, dass der Immunstatus nattirlicher Populationen j~ihrlichen Schwankungen unterliegt, die nicht mit Leukozytenz~ihlung wohl aber durch Quantifizierung der Immunoglobuline nachgewiesen werden k6nnen.U.S.

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