Weak correlation between haemoglobin concentration and haematocrit of nestling Great Tits Parus major and Blue Tits P. caeruleus

The possible relationship between haemoglobin concentration and haematocrit were studied in 14-days-old Great Tit and Blue Tit nestlings in central Poland.From basic avian blood physiology it was expected that the correlation should be positive but not strong.Our results support this expectation, as both blood profile parameters proved to be significantly associated but their relationship was relatively weak.However, haemoglobin concentration and haematocrit may show different sensitivity to ecological factors and thus are worth studying in concert.