The use of titanium dioxide as an inert marker for digestion studies in raptors

1. TiO2 is not a suitable marker for digestibility studies involving raptors. 2. Complete recovery of the 'inert' marker was not achieved. 3. Total collection of faeces is a more accurate method to determine food absorption. 4. Freezing sample solutions prior to colorimetric analysis can produce misleading results. 5. The percentage food absorbed from the intestine in Falconiformes is about 85% by dry weight.