Sunday 29 July 2018

Whats wrong with our Tawny Owl Nest Box?

Our Tawny Owl nest box was 'temporarily' retired last year because I hadn't designed it properly it was difficult to clean out the squirrel detritus.

This pic is taken while dangling precariously from a ladder approx 30ft up a pine tree. 
The box is full of sticks collected by squirrels, so no owls are going to use this... Ideally I would have designed it so that I wouldn't have to climb up another couple of extra feet to open the lid to clear it out, but I built it basically as a massive 'small bird box', and didn't scale up my lateral thinking facilities alongside.

Feeling creative I drew this up detailing all its other problems...

Its been on a 'to do' list for a while, and I was inspired by Kate Macrae's recent Tawny Owl Box re-build described here to get around to doing it.

To make matters worse, in an attempt to adapt it a little while ago, I took the side off (side facing in the diag above) to make a 'cleaning out hatch', and promptly misplaced the whole side.  It is now what could only be described as 'drafty'.  The front ledge fell off too...

Enter Tawny Owl Box v2
Its replacement aims to address all the issues described above, and add some more cameras with the requisite illumination (IR and visible light).  Probably.  Eventually.

Saturday 7 July 2018

BirdBox infra-red camera IR filter upgrade

Now that the bird nesting season is over, it's upgrade time! The infrared (IR) cameras in this year's boxes are getting IR filters...

and some to spare...

This year's two new bird boxes have an infrared (IR) camera with visible and IR LEDs (Robin box Birch log tit box).  There is 'night mode' with IR light  that the birds cant see, and day mode with optional visible light illumination. All non IR-light sensitive cameras have an IR filter built into the camera, whereas IR-sensitive cameras don't.

Without an IR filter, IR camera images have a pinkish cast to them in visible light, giving a permanent 'Hipstamatic' look:

Un-filtered IR camera pink colour is obvious here

An IR filter (called an IR-cut) converts an IR-sensitive camera into a conventional one that can't see IR light.  This gizmo has a bit of glass in it that blocks IR light, and can move backwards and forwards over the camera lens by changing the voltage polarity applied across it.

These bird boxes use the 8MP Raspberry Pi IR camera board.  This has a similar shape and design to those found found in many commercial CCTV cameras, so IR filters designed for CCTV camera modules can be fitted to them.  Sort of...

My first attempt to do this was the top-down camera in last years's double camera bird box.  Unfortunately, I sourced an IR-cut that had an ?M12 lens mount on it, basically a dirty great chunk of plastic poking out the font that needed to be cut off before I could use it = fiddly.  You can see my v1 test for this here from a separate project:

I wanted something easy to add to this year's boxes, and found an IR cut filter without a lens mount which fits nicely over the existing screw holes in the Raspberry Pi camera module (22mm separation).

This come from AliExpress (China, so take a couple of weeks to get to the UK), and costs $3.50 so wont break the bank.  It comes with a separate lens mount holder which I haven't used.  There's the option of 20mm or 22mm screw hole separation at order - you need the 22mm one as to fit the Raspberry Pi camera board.

This shows the underside of the camera unit that is slotted in to the top of the birdbox, pre and post IR-cut upgrade. The ir-cut is attached over the camera by M2 nylon screws and nuts, and the screws just go through the 4mm ply and pass through the camera board.

IR-cut sitting flush against the 'underside' of the bird box camera insert

I had previously designed this year's Raspberry pi zero W add-on board with an IR-cut in mind.  The voltage polarity reversal to switch the IR-cut is done with a L293DNE (£2.70).  I did  a more detailed writeup of this here which also has some example code.  The design for the wiring of this my customised add-on board is detailed here.

No birds in this, but you get the idea what switching the IR-cut in natural daylight does... there are alternatives to this, eg here which has integrated IR LED, camera and IR cut - does not have stellar reviews on amazon though.

Sunday 1 July 2018

How to make a Solitary Bee Box

We noticed a solitary bee using a gap between some tongue and groove wood cladding on the rabbit shed, which led to this bee house build...

The aim of most solitary bee house designs should be to...
  • Provide a safe place for solitary bees to nest.
  • Provide somewhere safe for new adults to emerge in the Spring
  • Allow easy access to cocoons for collection and cleaning at the end of the season.
This is my v1.0 bee house attempt:

Bee house in situ

Here is this some of the 2020 batch waiting to hatch in Spring 2021 

Here is a male hatching early season 2021.  I love the drawer since I can easily open it without much disturbance, it also makes filming this happening is really easy to do:

Hole-nesting solitary bees will use a variety of nest sites, all are variations on a long narrow opening into which nesting chambers are constructed.  Examples include:
  1. Bamboo canes: Variable sizes kept in a container of some kind.  Can source yourself or get online.  Disadvantages are you cant collect cocoons so allows disease, predator and parasite build up over time.
  2. Reeds: As above, but may be able to split to get the cocoons out.  
  3. Drilled blocks/logs.  Same issues as bamboo
  4. Cardboard tubes with paper liners.  **NEW** Update spring 2021, I got a starter set from, see here

  5. My holder in situ

  6. Stackable trays with pre-cut channels.  Channels cut into flat pieces of wood that are stacked, e.g., wildlifeworld.  This option came out on top, with cardboard tubes a close second.

Female bees collect pollen.  Female bee deposits the pollen in an appropriately sized hole.  She then lays an egg and closes up a chamber containing egg+pollen with a mud wall .  She repeats the process until the hole is full with multiple chambers.  In the Summer the eggs develop into larvae, feed on the pollen stores and develop into a cocoon.  In the following Spring the new bee emerges from the cocoon.  Males emerge first so that they're available to inseminate the females, who then go onto to perpetuate the life-cycle.

This v1.0 design is based on the stackable tray type.
  • Longer holes produce more females.  Females do more pollinating than the males (who hang about at the beginning of the season to inseminate the females then die).  We made 7.5 inch long trays, with the channels cut right to the end.  Some websites had examples up to 11 1/2 inches long, but I had limited timber stocks to work with!
  • Channels are 5/16 inch deep and 3/8 inch wide, which is the recommended size for mason bees.  I used this 1/4" square-end router bit.  I wanted a round ended (or 'bull nose') bit but couldn't find one the right size that didn't cost the earth.
  • Trays were cut from one piece of 18x199x2400mm pine (mixing imperial and metric, sorry), so I got 12 trays out of one piece.
  • Each tray has 8 channels giving 96 channels in total
  • Rather than routing these individually which would be a pain, I just routed the wood into one very long tray and then cut that into sections.
  • As the channels go through to the back, there's a piece of cardboard folded over the back end (as in this video).
  • The front of the block is unevenly scorched, as this apparently that helps them find the correct hole.  Other variations of this include marking the front, or using differing colour trays.
Stacked tray block before and after scorching
  • The stack is bound together by a tie down strap with metal cam buckle (I had to google the proper name for that) picked up from the local DIY shop, but can be sourced elsewhere.
  • There's an 'emergence drawer' at the base for any cocoons we collect this year (prob a bit late, may get a batch in for next Spring).  This gives a safe place for adults to emerge.  The holes in the front allow the newly emerged bees out (drawer would be closed...).
Safe place for new adults to emerge from cocoons in  the Spring

  • A South-Facing position is recommended, we settled for S-SE 

The effect of scorching is more obvious in this pic

The box housing the bee block is made from 'stuff lying about', but mostly is 6mm ply and finished with a coat of linseed oil.  No oils / preservatives are applied to the blocks themselves.

Most of the solitary bee info stuff that I could find in the web dealt with Mason bees, but there are many others which presumably have their own nesting preferences.

Some links that I found useful (watch them build, had a spot on Springwatch 2018) no tech in this one, but I like the idea of this bee counter discussion thread, which aims to count honey bees activity around a nest entrance hole using a raspberry pi camera... Could theoretically apply the same approach with a down-facing camera on this box...