How to use if else to get three outcomes in r

I have a large dataset of poultry. A subset of it looks like this:

>poultry
  Bird_ID weight_grams Year_weighed Alive
1 1_brown          855         2021     A
2 1_brown          850         2019     A
3 2_brown          852         2021     A
4 2_brown          848         2020     A
5 3_brown          851         2021     D
6 3_brown          850         2020     A
7 4_brown          620         2018     D
8 4_brown          580         2015     A```

I want to create a column to my poultry data frame and call it 'status'. This status column will indicate:

(i) 'New Big' if a bird used to have a weight <850 grams in one of the years it was weighed then grew to ≥850grams in another year and it has ‘A’ under Alive column, meaning it is still alive. 
(ii) 'Big' if a bird always had a weight ≥850 grams in all the years it was weighed and it has ‘A’ under Alive column, meaning it is still alive. 
(iii) 'Dead' if a bird has at least a ‘D’ under Alive column.

My desired output looks like this:

```> output    
  Bird_ID weight_grams Year_weighed Alive  Status
1 1_brown          855         2021     A     Big
2 1_brown          850         2019     A     Big
3 2_brown          852         2021     A New Big
4 2_brown          848         2020     A New Big
5 3_brown          851         2021     D    Dead
6 3_brown          850         2020     A    Dead
7 4_brown          620         2018     D    Dead
8 4_brown          580         2015     A    Dead

I have tried to work with dplyr pipes as follows:

  group_by(Bird_ID) %>%
  mutate(status = if((min(weight_grams) < 850) & (max(weight_grams) >= 850) & (Alive == "A")) 'New Big' else if ((Alive == "A") & (min(weight_grams) >= 850)) 'Big' else 'Dead')

Unfortunately this produces several warning messages which I don’t understand. I will be grateful for any pointers