I agree. It looks like a little Bourbon Red poult. I have raised one clutch of heritage turkeys, and they were raised together with chicks. The poults aren't born with all the instincts that the chicks have regarding eating, drinking, scratching, and dustbathing, so someone has to show them. Chicks act as great tutors, and the survival rates among poults are higher when brooded with chicks. The poult will be very dependent on the chicks for a few months, then will be as independent as them. Young turkeys really like to fly, and their wings grow faster than their bodies, so they get tremendous lift with those long wings and lightweight bodies for a while.
When I brooded them together, I just mixed the chick starter and the game bird starter together for ~24% protein the first 8 weeks, then changed the ratios to get 20% thereafter. It worked out great. It is very important to decrease the protein ratio after 8 weeks, as protein that high for either species can cause growth problems if continued too long.
Blackhead can be carried harmlessly by chickens, but it kills turkeys. It is very regional, so you can call your county extension office to see if it exists in your area. If not, there's no problem raising them together.
If the turkey is a hen, the young roosters will torture her always trying to breed, and she won't understand. Turkey toms don't run down their hens and grab them by the back of the neck while breeding. The toms wait for the hens to squat down in front of them, and balance on top of the hen by putting their long wings down on both sides of her during breeding. The turkey hens can be kept with roosters, but ideally no more than one. If she's not outnumbered she will probably be able to keep the boy at bay. If the poult turns out to be a tom, there shouldn't be a problem with the roosters. A rare tom may try to breed with a chicken hen, but that's not common, or safe. If a BR tom is allowed to get to full size, he has the potential to eventually weigh up to 33 lbs. My two toms are one year old and weigh 25 lbs and 29.5 lbs, so they would crush a chicken hen.
Other than that, heritage turkeys and Dorkings are very similar in their management. They both love to free range and explore, they both do best with more room than the average chicken needs, and they both love to fly and roost in trees if given the opportunity, but can easily be trained to return to their coop in the evening if free ranged. If you do plan on slaughtering the turkey, heritage turkeys are best slaughtered at around 9 months old, but will retain their meat tenderness for more than 2 years. Bourbon Red turkeys are considered the best tasting of the heritage turkeys, so it could easily be sold for a high price per pound if you didn't want it for your own table, or you don't sell it as a started poult. But be aware, turkeys are extremely personable, and it's very easy for them to turn into pets, especially when there's only one. Turkeys should never be kept alone, without the company of other poultry, but they can be kept with different species as flockmates.
I can't believe I didn't think turkey when you said there was a fuzzy little knob on the top of the head. The duck bill thing totally threw me off. Oh, how a picture is worth a thousand words. Was this poult a "free extra," or were you shorted a Dorking on your order?