Backyard Seed Dispersal: The Plot Thickens

After posting my last post I decided to do a little detective work. There are enough ripe Coprosma robusta fruits around so I picked several and took them apart to see what their seeds look like. Did they look the same as those I found the other day?

Unfortunately, the C. robusta seeds are not only much larger than my bird dispersed seeds, but a different shape. So I can confidently say the bird dispersed seeds I found a few days ago are not C. robusta, like I thought they might have been.  

Then, while picking up Saturday morning's walnuts from the back lawn, I came across some more bird dispersed seeds...

These ones look very much like C. robusta...

But what are these ones???

I tried cleaning off some the pulp off these new ones, and I did eventually succeed, but that pulp was horrible sticky stuff about the consistency of egg whites. It clogged up my tweezers something awful. As I was cleaning them, my mind drifted back to a university lecture I'd had a few years ago. Mistletoes are hemi-parasitic (i.e. they tap into their host tree to obtain water and nutrients, but they still photosynthesise to produce their own sugars). This means their seeds need to land on tree branches to be able to germinate and grow, instead of on the ground like most other seeds. What adaptations do they have to encourage their deposition on tree branches? They have sticky seeds. When a bird excretes a mistletoe seed (whether by regurgitation or defecation) it sticks to the bird instead of dropping to ground. To get rid of the seed, the bird must wipe it off on a branch. Although the sticky seeds I found were on the ground, I wondered if they could be mistletoe...

There is one mistletoe plant here at the farm (a green mistletoe - Ileostylus micranthus), which must have itself been brought in by the birds. So I went out to look at the mistletoe. It was covered in ripe fruit.  I collected several and pulled them apart, and this is what I found...

Seeds and fruit of Ileostylus micranthus.  Two seeds
covered in sticky pulp on the left and three whole fruits on the right.

This is very exciting – the host tree for our mistletoe is dying, and the branch the mistletoe is growing on already looks quite dead. As the mistletoe looks quite healthy one assumes the branch can't be totally dead, but its days are probably numbered. Hopefully the birds will successfully disperse one or two of its seeds to other trees, where they can germinate and grow new mistletoe plants.  

  

So we have bird dispersed C. robusta and mistletoe seeds but what were those original bird dispersed seeds I found? The mystery deepens!

A little seed dispersal treat...

Autumn is here as is evident from the increasing numbers of coloured leaves to be found...

...and an enormous array of toadstools which seem to have sprouted just about everywhere after some recent showers...

We also have an over abundance of apples, the excess of which the sheep are quite happy to consume, and a carpet of nuts beneath the walnut and hazelnut trees. Those nuts we miss picking up quickly become ratty's dinner, as evidenced by broken shells on the back lawn in the morning.

So this evening while I was scouring the back lawn for walnuts to pick up, I found...

For those more innocent among you, it is a bit of bird poop, full of seeds. Me being me, and perhaps because it conjured up memories of extracting seeds from monkey poo for my masters, this got me excited... here is an example of nature in action, ecology at work!

We get many fruit eating birds around here – a mixture of natives like kereru, tui, bellbirds and silvereyes and introduced species including blackbirds, thrushes and starlings - and little native tree seedlings popping up all over the place. And it got me curious... what sort of seeds are these?

Most of the seedlings we get seem to be Coprosma robusta and ake-ake – both of which grow in our garden. Ake-ake has wind dispersed seeds though, so I know straight away these seeds are probably not ake-ake. We also get quite a few kowhai seedlings, but these come in pods and I don't think the birds eat them, although both tui and bellbird love the nectar from kowhai flowers. The kowhai seedlings grow mostly underneath our existing kowhai trees, and have probably grown from seeds fallen beneath the adult trees. We also get koromiko, five finger and Pittosporum seedlings but these are a little less common, and very occasionally we get kaikomako, totara and even kahikatea seedlings. We even have a mistletoe that must have got brought in by the birds. Alternatively, these seeds could be a weed like Himalayan honeysuckle or hawthorn. But my top guess is that these are Coprosma seeds... not only are they common seedlings around here, but they are fruiting in full force at the moment too.

Coprosma robusta berries

Being on the back lawn, these seeds, even if they germinate are unlikely to survive. Even though our lawns are plagued with various seedlings, and some get rescued and planted out around the farm, most of get mown before they are big enough for us to transplant. So I decided to take the bird poo and plant its seeds. It serves a double purpose – the seedlings won't get mown off and I get to satisfy my curiosity and find out what they are. It perhaps even serves a third purpose – you can watch the seeds grow with me, and witness a little seed dispersal action. So stay tuned!