iNaturalist will be your resource for observation. It has tools to allow some nifty searching to both species and location. I recommend either Queens County NY, Westchester, NY, Kings Co. New York. New York City is not searchable, it sets to NY State. For this part you may need to search other counties in NY. Instead of starting with an observation of a tree or herbaceous plant in flower, start with the historical record, find a plant that interests you. If none come to mind here are some lists
Cornell Arboretum tree list
Have fun with the NY city tree map
There are less than weekly blog entries in NYBG ‘What’s beautiful now?’ Blog
NYC parks guide to blooming season
Once you have a species with historical records in the Hawthorne Valley Farmscape Ecology database (https://www.hvfarmscape.org/cms/ ) search for observations in NYC or the same location as the observation in the database (could be an upstate county). Note that iNaturalist collects all records, so you will have to look for the earliest records available within a year for the phenological trait you are looking for (flowering, full leaves, etc.).
This is rough, certainly look out your window, but most likely you will need to do some observations from some of the available livecam streams of bird feeders
Be creative, you might need to take a screenshot, then use MerlinID to identify your species. The composition will be different, youre much more likely to see red-winged blackbirds, more obscure sparrows. Continue as above to identify migrants vs. residents.