This indiviedual is acquiring breeding plumage. This species often goes under the name "Black-necked Grebe" in Eurasia where the nominate subspecies is found. It differs from North American birds in that it has a shorter bill and more white on its inner four primary tips. Canon PowerShot SX60.
References:
Cullen, S. A., J. R. Jehl Jr., and G. L. Nuechterlein (1999). Eared Grebe (Podiceps nigricollis), version 2.0. In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.433
Llimona, F., del Hoyo, J., Christie, D.A., Jutglar, F. & Kirwan, G.M. (2019). Black-necked Grebe (Podiceps nigricollis). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/52491 on 30 May 2019).