Infanticide Behavior Of Some Unmated SY Male Martins

[Chuck4]

I have an SY male in residence. He has not gotten a female partner yet. I hope he behaves if he doesn't. He does have himself a gourd though.

[Steve Kroenke]

Both our martin colonies are now under siege by many single SY males looking for territory/mates. This is a dangerous time for small featherless nestlings as some of the these males will commit infanticide by throwing out the young. It is CRITICAL that parent martins guard their tiny babies when SY males are trying to enter their nests. However, some parents will not do this and the small nestlings can become easy targets for SY males looking for territory/mates.

I am re-posting this older article with an updated photo of some small nestlings that were most likely tossed out by SY males over at Bob's colony. The gourd rack where we found these babies has several single SY males fighting with established ASY males.

Steve

[Anthony Neira]

So sorry to read what has happened to you & Bob, Steve. I'm VERY lucky not to have that & the attacks of female Martins by other males happen to me (yet!?). I know you can answer this question better than anyone else ( I have a permanent "Hoof In Mouth" Condition ! ), But really how would You answer a new Landlord's Question about "Is it EVEN WORTH IT "(?) to even get involved being a PM Landlord, with some of this sad situations about Females & newborns ? I (WE all here ) know the answer of course is YES ! , But again, I Totally respect your knowledge & experience, and rather let you explain. Keep up the Great work & best wishes, Anthony Neira

[-=DKC=-]

SY males are absolutely decimating my little 12 gourd colony this year. I have not witnessed any of these acts but all signs point to SY infanticide. I have a few SY floater males this year and one or two that are particularly aggressive.

Three days ago I found a dying ASY male under the gourd rack. Immediately had a SY male claiming the gourd of the dead ASY male and harassing the widowed female.

In the last 3 days all 7 hatchlings have disappeared from that nest as well as 5 more taken from 3 different nests. I found one newly dead hatchling on the ground about 15' from the colony but have not found any others. So I have now lost half of the 24 young hatched so far.

This is very discouraging and what a helpless feeling.

[-=DKC=-]

By the way, thank you, Steve Kroenke for writing this post as well as the many others on this subject that I found by searching. It at least helped me understand what I was dealing with.

[Steve Kroenke]

DKC,

I hope my article has been informative even though this subject of SY male martin infanticide behavior is rather disturbing, but unfortunately "normal". I have studied this behavior since the 1970s when I first observed it happen at my boyhood martin colony. The example I gave at the beginning of the article was from my boyhood colony.

It is most disturbing to watch this infanticide behavior as SY males throw out tiny martin nestlings though it is “normal” for them to do so. Sometimes I will find a small pink nestling still alive on the ground but usually they are dead from exposure to the hot sun or multiple fire ant stings.

Martin nestlings that are around seven days or younger are highly vulnerable to SY male depredations as these babies are small enough to be pulled or carried out of nests. The most vulnerable are those just hatched. SY males can “grab” the tiny baby by the head or body and carry the baby out of the nest.

As nestlings grow larger, then the SY males usually can’t carry them out but these males can sometimes try to “push” them out or inflict wounds on the youngsters’ heads and bodies.

In colonies where single SY males are most active in trying to find territory/mates, it is critical that parent martins of small featherless babies guard their young and keep these SY males OUT of their nests. The parents that are successful are the ones that develop a synchronized feeding system where one parent remains in the nest while the other seeks food. Unfortunately, many parent martins will not adhere to such a schedule and the tiny babies may be left unguarded for periods of times.

One of the most dangerous single SY males is one that is vocalizing loudly, pumping his wings, fighting with other SY and ASY males, making overtures to females and trying to force his way into nests with small nestlings. He may perch directly in front of the hole of a nest with small nestlings and vocalize while pumping his wings. This SY male really wants to find territory and a mate and is willing to fight for a nest, even one with small nestlings.

The most tragic cases that I have observed involve a widowed martin with small babies; her mate has disappeared and she is alone to face the horror of single SY males trying to take her cavity and claim her as their mate. These SY males are relentless in their pursuit of the female and may harass her for hours as they try to get to the babies to throw them out. She will fight these males fiercely but she has to leave the nest to find food for the young. This is what any SY male that is after her is looking for. He will quickly enter the nest cavity and usually starts to carry out the small nestlings one by one. If he succeeds, in most cases I have seen, the female eventually accepts the “killer of her young” as her new mate! They often raise a family together if there is enough time! In other cases, the nestlings may starve or become severely malnourished because the female is constantly guarding them and trying to keep the SY male away. I have NEVER seen a widowed female accept a SY male as her mate when her babies are still in the nest.

Right now in our two personal martin colonies, mine and my neighbor Bob, we have single SY males "working" our gourd racks and houses and I just cringe when I see a super aggressive one trying to enter cavities with small featherless babies. I just try to watch my colony closely and look under the gourd racks/houses frequently for the "pink" babies on the ground. If I can get to them before the fire ants and the hot sun does its damage, I can place them back in a nest.

I wish you the best and hope the SY males in your colony finally calm down and leave your nestlings alone!

Steve

[-=DKC=-]

DKC,

I hope my article has been informative even though this subject of SY male martin infanticide behavior is rather disturbing, but unfortunately "normal".

Hello Steve. Yes, I read about 10 of your past posts about the issue. They did help very much. At least I now know what is going on and what to expect.

I think that if I have a widowed Martin with young next year I will try to move them to other nests. At least they'll have a chance of survival then. It's heartbreaking to spend so much energy controlling House Sparrows and removing caps from eggs only to see the entire clutch be killed by SY males.

Next year I also may try to add a couple of additional gourds for the late SY males if any are this aggressive.

The parents that are successful are the ones that develop a synchronized feeding system where one parent remains in the nest while the other seeks food. Unfortunately, many parent martins will not adhere to such a schedule and the tiny babies may be left unguarded for periods of times.

I call this "tag-teaming". My pairs who are taking turns guarding their nests are doing much better than those who do not.

The most tragic cases that I have observed involve a widowed martin with small babies; her mate has disappeared and she is alone to face the horror of single SY males trying to take her cavity and claim her as their mate. These SY males are relentless in their pursuit of the female and may harass her for hours as they try to get to the babies to throw them out. She will fight these males fiercely but she has to leave the nest to find food for the young. This is what any SY male that is after her is looking for. He will quickly enter the nest cavity and usually starts to carry out the small nestlings one by one.

Sadly, this is what has happened at my colony this year.

I just try to watch my colony closely and look under the gourd racks/houses frequently for the "pink" babies on the ground. If I can get to them before the fire ants and the hot sun does its damage, I can place them back in a nest.

I've been looking multiple times a day but unfortunately, the SY males have carried all but one of these young off of my property.

I wish you the best and hope the SY males in your colony finally calm down and leave your nestlings alone!

Steve

Thank you. Today the aggressive male is sitting on the widow's porch and singing. So hopefully he will mind his own business now that he has successfully claimed a gourd. And thanks again for your posts.