Hello to all,
I 've currently analysed pellets from Lesser Kestrels throughout different seasons. I think that would be worthy to make some correlations with the prey body mass. I have some data from insect reference collections but I still need more. I would be greatfull if anyone knows where can I found data about European Ground beetles (Carabidae) weight.
Thanks in advance!
Konstaninos Vlachopoulos
Dear Konstaninos Vlachopoulos,
You can find information on body length for European Carabidae on http://carabids.org/. They do not have information on body weight, but I used the power relationship by Rogers et al. (1976) to calculate body weight from average body lengths in insects:
Rogers LE, Hinds WT, Buschbom RL (1976) A general weight versus length relationshop for insects. Annals of the Entomological Society of America 69: 387-389.
If you decide to use body length as an approximation for weight, you might find the missing body length data in the Fauna Germanica books by Reitter (https://archive.org/details/faunagermanicad00reitgoog). These identification keys for Coleoptera are in German but most of the times the size information is given directly at the last identification step to the species.
Hope this helps,
Nadja
Dear Nadja thank you very much, for your contrtibution, I am really grateful!
Konstantinos
Hi, i think you should rather use body weight instead of length. Here you can find equation how to link length and weight
https://www.researchgate.net/publication/232724744_Local_and_regional_interspecific_abundance__body_weight_relationships_of_ground_beetles
good luck
Article Local and regional interspecific abundance – body weight rel...
I attach a paper with table of average dry weights of several species of Carabids established by weighting of large amount of individuals.
Calver MC and Wooller RD. 1982. A technique for assessing the taxa, length, dry weight and energy content of the arthropod prey of birds. Aust. Wildl. Res.
Rogers LE, Buschbom RL, and Watson CR. 1976. Length-Weight Relationships of Shrub-Steppe Invertebrates. Annals of the entomological society of America.
Direct measurements are better than calculations, but that is obvious. A few small points: first and foremost, it is body mass (in g or mg), not weight. A very common mistake in the literature, but an unequivocal mistake, so always use the term body mass. Second, body mass data are unbiased only if they originate from live specimens, or live traps. If pitfall traps with a fluid are used to collect beetles, measurements are biased. This may be the case with Zbysek's data - but he can confirm that. I cannot tell you offhand how biased, but it is easy to realise they are. If you have to estimate body mass from length, and cannot do direct measurements yourself (perhaps possible, by measuring elytra) - books usually give a range of body length.Make sure you check that the length in the book and in the equation are identically measured (cannot be taken for granted). And if body length intervals are given, I'd use the geometric mean not the arithmetic one.
Of course there are many possible biases, like the time, when the beetles were captured (females with or without eggs, individuals after starvation etc.), individuals from mountains can be smaller tah in lowlands (a good example are Carabus violaceus or Abax paralelopipedus). The individuals from a habitat with better food offer can be heavier. The formol can be bound on proteins and can increase the body mass. All this is or can be true. But with some mistakes or rather a variability width there are general tendecies and it can be estimate how much energy the eaten individuals contained.
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