Although behavioral studies demonstrated light-induced rnagnetoreception in the insect Drosophila melanogaster, gaining insight into the possibility that a radical-pair mechanism accounts for the magnetic response of the cryptochrtome (DmCryl) is complicated by a number of factors. In addition, the mechanism of magnetoreception for the cryptochrome from the garden warbler bird Sylvia born (gwCryla), which demonstrated a long-lived radical pair by transient optical absorption measurements, has also not been rationalized. To assess potential feasibility of a radical-pair mechanism in DinCryl and gwCryla, formed by excitation and electron transfer between a Trp-triad and flavin adenine dinucleotide (FAD), further separated by electron transfer within the triad, we applied a combination of theoretical methods, including homology modeling and molecular dynamics (MD) for structure refinement, high-level ab initio theory, and MD simulations using a polarizable force-field for prediction of pKa and the electron transfer rate. Calculated excitation energies, followed by electron transfer in model compounds of DmCryl that assume proton transfer in conjunction with electron transfer from Tip (W420) to FAD and the predicted pKa for the proximate residue to FAD (Cys416), support a radical-pair mechanism. Furthermore, free-energy and reorganization energies for the Tip-triad in DmCryl demonstrate facile electron transfer, explained by the local protein environment and exposure to solvent, which in turn enables a large enough distance separation for the radical-pair partners. Results for gwCryla demonstrated the importance of accounting for relaxed excited-state geometries in validating the first stage of a radical-pair mechanism. This work provides insight into the so-called chemical compass mechanism to explain magnetic-field sensing in DrnCryl and gwCryla, expanding on previous work on the cyrptochrome from the plant Arabidopsis thaliana (Solov'yov et al. J. Am. Chem. Soc. 2012, 134, 18046-18052. Solov'yov et al., Sci. Rep. 2014, 4, 1-8.).