In many Harvest Moon games, one becomes very attached to the Animals on your Ranch, whether poultry, livestock, transport animals or pets. It always is a wrench to be confronted with a death event.
I try to be philosophically at peace with the idea of life in death and death in life but when it comes to Harvest Moon and my animals, I really can't bear to see them die. I therefore sell them instead.
Like FoMT/MFoMT and HM DS/Cute DS, in Island of Happiness, every ranch animal has a set life expectancy. A Chicken's life expectancy traditionally is the shortest and IoH is no exception. Your Chickens will reach the natural limit of their lives on their 4th Birthday. From that point onward, death is loaded randomly into the game when you awaken.
As with other Harvest Moon games, I suspect that the likelihood of the occurrence of the Death announcement will become more probable the longer the animal avoids the Grim Reaper. In previous HM games, I stubbornly held onto to Animals a year after they reached their life expectancy. Sometimes I would be required to reload the game five or six times before I was able to obtain a morning without a graveyard scene embedded in it.
When I experienced the death of my oldest Chicken at age 4 in Island of Happiness, I reloaded and greeted the dawn again. The event did not re-occur. Rather ironically, I rather wished to experience it again in order to write down the precise text and capture a screenshot of the solemn announcement... The first time it occurred, I was so horrified that I moved through it as quickly as possible and then reloaded at once.
I decided to sell my first chicken instead of allowing the event to occur. With Denny and Lanna finally married, I need to begin a new game in any case, surrendering the test game. I've held onto it far too long. In fact, I need to overwrite the game myself probably to avoid any temptation to keep playing it... I've had to do that in the past with other games.
To be honest, the second game always is more enjoyable for me than the first when playing Harvest Moon. I know what mistakes to avoid and am a little more relaxed, knowing what I can expect to achieve and what is unreasonable at any point in time.
Furthermore, it is the second game that actually creates a good guide, as events are replayed with more concentration.
To return to the topic of Death, though, it is Taro who will make the announcement whenever an animal dies, whether of sickness, neglect or simple old age. If you neglected the animal, he will scold you. If the animal died of old age, he will tell you not to be discouraged, that death is natural and cannot be avoided. Little does he know. I avoided THAT death by selling the bird to Mirabelle the day before she celebrated her 4th birthday (the day on which she had met her demise in the first place!).
Life expectancy for Chickens is 4 years. It usually is one more year for Sheep and another for Cows. That would make it 5 years for Sheep and 6 years for Cows. I haven't proven that yet, but I have confirmed that the Chicken can expect only to reach her fourth birthday in peace.