Bird strike tests are difficult to conduct, time consuming, and very expensive. Therefore, computational methods have been favored to reduce the number of bird strike tests and to speed up the design process of aircraft structures. The present study employs a computational approach to gain insight into impact dynamics of such highly deformable impactors as birds. A bird impactor model is constructed based on a smoothed particle hydrodynamics (SPH) and implemented into the LS-DYNA software. Finite element model of aerospace-grade aluminum plates of different dimensions is used in the simulations. Convergence tests are performed and results are compared with the experimental data available in the literature. The effects of critical parameters such as impact velocity, impactor mass, and plate thickness on the impact force are examined and discussed. In addition, the results of numerical simulations are cast into nondimensional parameters which are subsequently placed in the so-called impact characterization diagram. The characterization diagram which is originally proposed for rigid impactors gives the normalized maximum impact force as a function of three nondimensional impact parameters. The present study evaluates the efficacy of the characterization diagram for the case of deformable impactors (birds) modeled through the SPH method. It is determined that the diagram can be used with reasonable accuracy for the case of highly-deformable impactors.