Auckland winter monarchs

August 2026

We are truly into winter now. Cold nights. Some cold days too (that's Auckland cold, not South Island cold). We are experiencing our coldest nights so far - down to 1 degree Celsius. Given the assurances that this garden never got frost (which was certainly true of my Hillcrest garden), I chose my plants heedless of near freezing temperatures. We shall see if everything comes out the other side in spring.

Weeds never looked so good! Jack Frost visits the butterfly garden.

I have noticed that even on warmer winter days, Auckland's air temperature does not reach the threshold for monarch activity until late morning. However monarchs are coming out on the sunniest days into the garden, and when the conditions are right, I have at least two monarchs around. This is wonderful, because we are in a valley and the sun takes its time reaching us in winter. Whilst I've released red admirals over the winter months, I haven't seen any in the garden.

A male and female monarch feeding from Buddleja × weyeriana on 23 July

Last winter I reported not seeing any monarchs on sunny days, so the expanded butterfly garden has made a difference. Hooray! Mostly, the monarchs in the garden are not ones I've raised, tagged and released. It means that elsewhere the monarchs have escaped their predators. I was talking to a friend and she has monarch caterpillars of various sizes on her Auckland swan plant. The ones in my garden have not been so lucky.

I've had female monarchs laying eggs on the sunniest swan plants sporadically throughout autumn and winter, yet caterpillars are not making it to pupation. I suspect that ants have taken most of the eggs and maybe the newly emerged caterpillars. There are those tell-tale small holes of early caterpillar feeding on the leaves, but no caterpillar in sight. The invasive wasps have definitely gone for now. They will come out again in September and the battle will be back on.

Egg laying on 10 July. The air temperature was 14 degrees just before midday.

So despite the fact it is mid-winter, I still have butterfly castles outside to raise monarchs under protection. It also means I can tag the monarchs when they eclose for the Moths and Butterflies of New Zealand Trust tagging project. I have released three in mid-July with tags on their wings and four this first week in August. If you are local, keep an eye out for them. I have no idea where they are spending the time in between visits to my garden. That's what the project is all about. I have not spotted them sheltering in local trees and they must be somewhere near.

It was nearly three months between my last tagged butterfly sighting in the first week of May and one last week. It was lunchtime and I escaped the work laptop for a wander around the garden with the puppy on a lovely sunny day. On the tree dahlias - sourced from the Moths and Butterflies of New Zealand Trust cutting sale - was one of my own monarchs released 11 days earlier. It was such a joy, firstly because you don't know in this varying weather if they are surviving and secondly because I still check every monarch I see for tags. That's a lot of monarchs in three months that haven't had tags.

Using the phone camera to ID monarch tags. This female monarch is on a tree dahlia flower.

I have been asked how I see the tags. I don't have the best eyesight, but I tune in to the colour discrepancy on the wing as they fly - the white stands out against the colours of the underside of the wing, even when the wing has faded to tan - you get a sense that something doesn't look quite right. I then stalk them with the camera app on my phone. I can only get the tag numbers by zooming in hard - you simply can't get close enough to read the tag without help, even in winter.

Watching some of the monarchs around, they are only just functioning when the sun is out, but the temperature is still low. I watched a female have difficulty holding onto plants and I was actually able to pick her up and move her onto the flower heads of tropical milkweed where she had a long feed. It goes to show how important winter nectar is. I was worried that I would not have enough flowering to support a winter population, but they seem to be feeding less regularly, and sun-basking a lot, so the plants I have already are adequate. That said, I want to get my hands on the winter-flowering buddleia, Buddleja salviifolia, to take the pollinators through late winter and early spring. It is not as visually appealing as the summer and autumn flowering buddleias, but the bees and butterflies won't care. It will give me peace of mind as several of the plants that fed the butterflies from late autumn and through June and July are finally going over.

Female monarch butterfly feeding from tropical milkweed flowers

I was ready to report that Auckland monarchs had finally joined their compatriots down the country and paused their lifecycle, but I found another lot of eggs last week and a few have since hatched into tiny caterpillars. I start them off inside, because there is the risk of anything outside being blown over or away. They will go outside when they reach the third instar and I can't keep up with their appetites. Because only a couple of the swan plants are having eggs laid on them - in the sunniest spots in the garden - I have plenty of plant material going spare to raise the hungry caterpillars on.

It will take a long time before they emerge as butterflies and I am not sure that I will use all the tags I have on my sheet before we are into spring. However, just as it was fascinating to find out about the movements of the monarchs that were tagged in early autumn when things were still quite busy, it will also be interesting to push the exercise into spring, when they become more active again. Will butterflies that overwintered further down the country then travel once things are warming up, or will they stay put to finish off their lifecycles? Do butterflies only travel - if they travel (we know the majority don't) - early on in their life or will older butterflies travel too? The results from this year's tagging will be fascinating. I had a look at the map which shows all the butterfly journeys recorded so far and there is one butterfly that flew across the Cook Strait! Or is that blew across? There is an interesting story there!