Found a mouse nest on top of my air filter. Material looks like dryer lint (though there are specks of color in there). Is it likely that the mouse made its nest out of materials external to the car, or could this be from inside the car? And if so, what might it be?

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 178k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 75k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife